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: 
Yes, real Levi's still go for considerably more in foreign countries than in the US, in official shops. Like 501s are usually under $50 in the US, and over $100 in Australia. This is partly historic, partly due to currency fluctuations and the dollar being down at the moment, and partly due to VAT/GST.

No, you will not easily find someone to buy your one pair of jeans in a random size at those same prices. Wouldn't you just buy them from US eBay if you were them?
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.