Question: Some years ago, particularly before the 1990s, there way a saying in Europe that (paraphrased) you can sell your blue jeans in every part of Eastern Europe and literally live like a king for a week.

Naturally things have changed since then. But is it still possible to do so in any part of Europe?

Answer: 
That used to be true, back in the 1980s, in the Soviet Bloc countries, because:

* blue jeans were *the* fashion trend then and there
* they were not available on the market, *at all* (not "sold out", not "in small quantities", not at all.)
* thus providing an opportunity for home-made imitations *and* for scarce (rare even) black-market goods

Now, that's a textbook example for Economics 101: high demand, extremely scarce supply - and prices shot through the roof, quite predictably: and yes, people were willing to part with a month's worth of wage to get that one pair of jeans (as @M.K. recalls in the comments). So, it indeed used to be true, *literally*: sell a pair of blue jeans and live like a king for a week.

Things that have changed in this situation since 1980s: 

* Everything.

No, seriously:

* Jeans are not *the* new hot fashion trend (perhaps *a* fashion trend, if at all)
* Import is unrestricted
* Supply is abundant
* And that all was true even before I could have ordered virtually *anything* from *anywhere*, directly, through the Internet.

In short, that specific bubble has popped not "some years", but twenty-some years ago; *two* major market changes ("paradigm shifts," if you will) have happened since. It's an amusing historical tidbit, but nothing more.
It used to be the thing to travel to New York for the weekend and come back with a suitcase full of Levi's (nonchalantly avoiding the red channel).

Looking at Levi US and EU\_GB sites, I see the prices for the classic 501 is from $44 or £70 ($112). However, mid-nineties saw the emergence of a large grey market. I guess you only pay the high prices to buy from posh shops. If you are going to try to sell jeans from a suitcase in a pub, you'll have to significantly undercut the legitimate greymarket, and you'll presumably need to pay duty on the imports (don't break the law!).

I understand that in the US Levis are considered an everyday, working brand. In the UK they are considered a fashion brand, so they can command higher prices, and someone has to pay for the advertising. 

[I only wear sensible trousers from M&S.]