My dad and I started collecting them back in the late 90's as a hobby for us to do together. We got really involved in it and almost started dealing them. Glad we didnt now though. For every birthday, fathers day, Christmas, etc thats what we gave each other. Plus we bought alot of them ourselves too. I would say that I have personally spent $3k or so on diecast just myself.
About 2 years ago we slowed down alot and now really only buy the cars we really like mainly b/c it did get really expensive. I have alot of Force ofcourse but I actually mix it up some. I have the Force 100 Wins car, the 96 Force Driver of the Year car, Steve Kinser's #11 World of Outlaws Sprinter, and Tony Shoe's 99 Exide TF Championship dragster all in a case signed in my office at work. Also Blaine Johnson, Bob Glidden, and Mark Martin. You'd be surprised the people who actually know who they are.
I still say the best place to buy them is ebay, you can get them alot cheaper than at the track or from a dealer. Hopefully by Dallas Mike Ashley's car with Evan's face will be out in diecast b/c thats the one I really want now.
Force's Race Station has alot of stuff but like stated earlier, there's hardly a diecast there under $100.