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.
Not anymore. Now you'd have to sell a blue auto...

Nowadays you can buy a heck of jeans of various quality everywhere, from marketplaces to supermarkets. The prices in, for example, Poland, are much lower than in Germany, so you'd have more luck selling your jeans in Germany...

Before the 1990s the situation was completely different. Almost everything was hardly available (there are various photos of markes shelves, where there's only vinegar on it). Some products, like jeans, were possible (officially) to buy only for dollars and the average citizen wasn't allowed to buy dollars, so such products were available only to people having relatives in the West, or buying it second hand, for the high price. 

Now most Eastern Europe is in EU, and the rest trade intensively with the west, and the dollars are widely available, as well as the goods from all over the world. And jeans comes mostly from Asia. Such curiosities as internal export (see Pewex) are known only to older people, for the yougsters they are like knights and dragons.