I've paid a lot for guns I really wanted, but it's a relative thing.
The most expensive gun I own at present (SIG P49) cost me $2600, and I had to hunt around a bit to find one with a holster, extra mag and the right condition at that price. Nothing particularly special about it, but that's just the going price for one these days.
My late father would have disowned me had he seen this particular price tag, but then the current price for a decent sheet of plywood would have given him a stroke anyway.
Paying $1K for a gun has become a relatively frequent thing for me lately. Fortunately, I have enough slack in my budget right now to do this a few times a year. Not everything I buy is in collector-grade condition, but occasionally it makes better financial sense to hold out and pay more. The subjective part is how much more one is willing to pay, and there is no one answer.
I can say that inflation would really have to do a number on the US dollar for me to spend over $20K for anything less than a car.
Incidentally, when I was talking with a couple of shooting buddies last week, I remarked that a typical $200 used gun from the 1990s costs closer to $700 today. The other two guys nodded in agreement. That end of the price scale is much more relevant to me.