Most people don't see what's going on now days. world coins were never really "cheap" per se but were merely not widely collected in their countries of origin because the middle class is where most coin collectors reside and the middle clkass in many countries used to be nearly non-existent. Take India with a population of 1.2 billion people. Most India collectors were in the US until recently but the middle class in India is exploding. They have an excellent educational system and the economy is growing in leaps and bounds. Now they want Indian coins because most newer collectors prefer the coins from their own country. In twenty years these exact same collectors will be seeking world coins but for now they are concentrating on India. All the old Indian coins are in great demand and the supply is adequate to keep prices from exploding so far. The demand is putting pressure on many prices but few are having dramatic increases because there is deep supply of old Indian coins in the US and elsewhere. But no such supply exists for modern India because nobody collected these. Attrition has been staggering and supplies are nearly non-existent for some coins. This is making the prices of modern India explosive as significant demand is met with almost no sipply. This same thing is going on all over the world but is most visible in those places where the middle class is exploding. I've been trying to buy Indian proof sets for decades but they are seldom seen. Now they are seen only slightly more often but they are sporting a far far higher price.
BTW, the "American coins are bigger" post was in refference to the tiny picture. It's hard to be sarcastic on-line. Hopefully no one was offended (even by the tongue sticking out). This issue of collecting American (more properly USA coins) coins has come up before and I have thought about it a lot. Popularity of something is hard to predict (or I could be wealthy). Why is cricket popular in Britain and India and not many other places? Why is soccer popular in most of the world and not in the USA (comparatively)? Why is American Football not popular in other places? In most cases we just have to shrug and go on. I would venture to say that collecting coins of a country is more popular in the particular country in question. I would not expect any other country to have a majority of collectors collecting American coins in any other country than the USA, just like I would expect the majority of collectors of German coins to be in Germany. You guys who collect ancients are in a world of your own. Now, if the hobby is popular, it should follow the demographic of the country in question, "all other things being equal". By that I mean that the hobby has to first catch on and then watch out. I see China becoming a world force soon, and not necessarily for American coins. The fact that American coins are widely collected is evident if you do a search for the world's most expensive coins. Of the top 10, 8 are American coins, and of the other two, one of them is that odd kilogram Canadian "coin".