Bingo. And once Leopard ships, the number of people still using 10.3 is going to go down even further.
I also believe that if you have a PowerPC Mac, and you bought 10.4 a while ago separate from your Mac, and you now buy Leopard, you can then sell 10.4 on eBay (after removing it from your Mac), so there should be cheap and legal copies of Tiger on eBay soon. Same as you can buy Panther quite cheap now.