This usage is informal but not incorrect .
I wouldn't use it in official business documents, but it can be freely used in speech or less formal contexts.
While statements like "seventy-three hundred" are rarer than their equivalents for numbers below 2000, they're perfectly intelligible and frequently used.
english.stackexchange.com/users/48/JSBձոգչ
I work in a building at '4400 North First Street'; I'd never say anything other than 'forty-four hundred' for the address.
It is perfectly grammatical, and often very sensible.
english.stackexchange.com/users/2386/Jonathan Leffler
It is certainly proper grammar.
From my experience, referring to four-digit numbers in the hundreds is more common in the US than in any other English-speaking country.
As for 7300 , seventy-three hundred is perfectly correct to say.
It really all boils down to the speaker's choice.
I must add, though, that for those numbers with three zeroes, thousand is preferred to hundred .
Thus, 3000 is better called three thousand than thirty hundred !
english.stackexchange.com/users/2705/Jimi Oke
In some places, city blocks are always referred to in terms of hundreds.
For example, in Chicago it is normal to hear somebody talk about driving from the twelve hundred block to the seventy three hundred block of some street.
This means going from a block with addresses of 1200-1299 to a block with addresses 7300-7399.
It only works in cities with a regular grid layout where each street covers a range of exactly 100 addresses, but in that case the "hundred" is the basic unit, rather than the individual addresses themselves.
So, you can sort of think of twelve hundred being grammatically analogous to twelve kilograms or twelve apples.
In general, I never encounter it in formal written documents.
The only time I see it in writing is when somebody wants to explicitly capture a speaking style, such as an exact transcript, or dialog for a play.
However, when reading a document out loud which says "7300," it can sometimes be idiomatic to pronounce it as seventy three hundred instead of seven thousand three hundred. ("Our Chicago office is located on the seventy three hundred block of Wabash street.")
english.stackexchange.com/users/3268/wrosecrans
I can't exactly answer but I can add that Steve Jobs is often heard talking about numbers in that way during his public keynotes.
So I would say that it is proper business practice, at least orally.
english.stackexchange.com/users/3264/FrenchFry
I worked for a bank for 16 years.
We were taught that for writing checks, for an amount of $1200, the textual amount should be One thousand two hundred, not twelve hundred.
english.stackexchange.com/users/87461/Edward Moneo
Not that Jeopardy! is the ultimate authority on such matters, but you can hear the "XX-hundred" format used four times in just over 30 seconds in this video clip – twice by the contestant, and twice by the host.
Clearly there's nothing wrong with this usage, and, in some contexts, it simply rings and flows more naturally than its "X-thousand, Y-hundred" counterpart.
english.stackexchange.com/users/18220/J.R.
Sometimes you will hear people refer to four digit numbers in terms of hundreds. For example, sometimes people will say fifteen hundred when talking about the number 1500. Is this proper?   What are the rules of usage? In my personal experience, the hundreds notation is common for values less than 2000, but rare for larger values. Can I refer to 7300 as seventy-three hundred?  I know this has been discussed in  another question , but that was in terms of years. I'm asking about numbers in general.
Is it proper grammar to refer to four digit number in hundreds?
english.stackexchange.com
<numbers>
english.stackexchange.com/questions/7953
english.stackexchange.com/users/1982/epotter
Referring to four-digit numbers using hundreds is informal but not incorrect. It may not be used in business documents, but usage will really depend on the speaker's preference. However, when a number has three zeros, such as 3000, it is much better to call it three thousand than thirty hundred. It's possible that this phenomenon is more common in the US than in other English-speaking countries. The use in the sample sentence is an informal use, but it is correct and some people believe it can be used on official documents. While statements like "seventy-three hundred" are rarer than their equivalents for numbers below 2000, they're perfectly intelligible and frequently used.It can come down to a question of personal choice. Some people, however, have not seen it in formal written documents. Some people have only seen it in writing is when somebody wants to explicitly capture a speaking style, such as an exact transcript, or dialogue for a play.  It is sometimes used in grid layout cities. Somebody, for example, working in a building at '4400 North First Street'; might only say 'forty-four hundred' for the address.  
Referring to four-digit numbers using hundreds is informal but not incorrect. It may not be used in business documents, but usage will really depend on the speaker's preference. However, when a number has three zeros, such as 3000, it is much better to call it three thousand than thirty hundred. It's possible that this phenomenon is more common in the US than in other English-speaking countries. Grammatically correct but informal
This usage is  informal  but not  incorrect . It may flows more naturally than its "X-thousand, Y-hundred" counterpart. Although it might not be suitable in official business documents, it can be freely used in speech or less formal contexts.  However, this is largely down to the choice of the speaker and is also more commonly used in the US than in other English-speaking countries. This form of speech is generally considered to be grammatically correct but informal and its use will be the choice of the speaker. However, this style would be unusual to find in written documents, but it is often used when referring to addresses. This form of speech may also be more common in the USA than other English-speaking countries. "Seventy-three hundred" is a perfectly acceptable way to say the number 7,300.
We were taught that for writing checks, for an amount of $1200, the textual amount should be One thousand two hundred, not twelve hundred. Not seen in formal written documents It is perfectly grammatical, and often very sensible.
We were taught that for writing checks, for an amount of $1200, the textual amount should be One thousand two hundred, not twelve hundred. Not seen in formal written documents It is perfectly grammatical, and often very sensible.
This is an informal use, but it is correct.It can be used i official documents. While statements like "seventy-three hundred" are rarer than their equivalents for numbers below 2000, they're perfectly intelligible and frequently used. It can be personal choice. It is used in grid layout cities. Not seen in formal written documents The only time I see it in writing is when somebody wants to explicitly capture a speaking style, such as an exact transcript, or dialog for a play.   In banking circles, the pronunciation varies.
Informal but not incorrect. It is grammatical.
This form of speech is generally considered to be correct grammar but informal. You would be unlikely to find this style of language in written documents, but many city blocks are referred to in terms of "hundreds". "Seventy-three hundred" would be considered a perfectly acceptable way to say 7,300. This form of speech may be more common in the USA than other English-speaking countries. Whether or not this speech is used will be subjective.