I've spent well over $800 in the last 7 months. And I focus my collection on a theme!
But I splurged on others before I decided to collect just AKs. I can only imagine how expensive it gets when your interest is more general.
Be careful looking at them as investments, though. If you plan or need to sell them, do it while they're hot. They are valuable only as long as there's a market for them.
If you want investments with a more certain future just trust spending your $6.50 - $15.00 per pin on stocks or even EE Bonds instead.
Just my two pennies based on my personal experience with the Beanie Babies.
Wanda