I'm a cheapskate when it comes to buying kits. The most I've spent on a single kit is the Tamiya 1/25 scale Tiger I for around $50 in 1991. Of course, I had just come from an all-expense paid vacation at an exotic location where I had limited chances to spend any money, so I figured I'd splurge.
Even in today's uber-kit market, I stay below the $40 mark for a single scale model kit.
Now, if you branch into the R/C model area, I did buy the Tamiya 1/16 scale M4 105mm remote control tank. I think that one was in the $200 range, but very reasonable for an R/C model. I also won the 1/16 Tamiya full R/C Tiger I. I did not pay for it, but it retailed for $750.
I do know a couple of people who have spent loads of money on vintage kits. I just sold a couple of small, but rare/vintage kits for $224 and $310.