I figure there were maybe 500,000 of these bookshelf games produced in the 1968-72 time frame. If 10% survived to today there are 50K around. eBay has 6 million users, say 10% of the US online population so maybe 5,000 games could be brought to market today. OF those maybe 20 % would be collecter quality. So, you accumulate the 1,000 games at an average price of $50. (Today the game costs $20-30. By the time you bought the 1,000 the price would have inched up to $100) Then, you have "cornered" the market. (I know if you try to sell them for $1,000 a piece then more would come into the market from people's attics). But you sell them at $150 and make 200% return on your investment.

eBay has many possibilities for experimenting with econ 101 :-)