Definition: In this task, you are given a Reddit post as a text. Your task is to generate a title for this text. The title should start with "TIFU by", followed by a situation that caused humor. The title should contain 7-12 words, ideally.
Input: Text: background - i own a heavy equipment dealership, and my focus is on new and used excavators.

one of the new equipment lines i carry has an unusual pricing structure, as in, the invoice on a machine may be $50,000, but upon selling it they give you $5,000 back.

i like to make 10% on a machine, so that $50,000 invoice will sell for $55,555.55, so i round down to $55,500. however, i'm extremely competitive, so i throw the customer half of the money i'll get back from the supplier, making the price only $53,000, and my true cost is now $45,000. doing the math, i'm making $8,000, with a true margin of 15%.

well, now for the tifu. the supplier recently updated their pricing structure, so that the money they used to give you after selling a machine, would just come off the price of the unit when you order it. so my invoice no longer shows $50,000, but $45,000.

well, i fucked up big time, i completely forgot the new invoice ammount is the final price, and forgot that i don't get anything off later, so i do the math $45,000/.9 = $50,000-$2,500 = $47,500. (i'm thinking $45,000-5,000 = $40,000, thus making $7,500, not $2,500.)

the customer is looking like they're going to walk, and i calculate that a true margin of 15% lands me at roughly $47,000, so i decide to bite the bullet and give him another $500 off, still keeping my margin, and making great money.

so, we shake on it, i hand him over to one of my sales guys to do the paper work, and about half an hour later, after the customer left, it hits me ... oh fuck!

 
i play the new game by the old rules, costing me $5,000 in lost profit.

TIFU by not double checking my math.