I voted for up to 3K. Usually, I hunt for deals, but I will spend some money on the right amp. The most I've ever spent ($3200.00) was on my DST-30, which is a very nice hand built early AC-30 clone. It has proven to be worth every penny I paid for it. I even just found a second Goodmans Audiom 60 speaker for it, so it will have some circa 1962 speakers in it soon.
I also bought a brand new JTM45 reissue in 1988. I still have it, and it's proven to be a great amp over the years.
Some others include a 1973 Marshall 1987 50 watt, 1978 Marshall JMP 50, 1979 Marshall JMP 100, 1986 Hiwatt 100R, 1964 Fender Bandmaster, 1970 Fender Deluxe Reverb, 1965 Ampeg Gemini II, and others. The way I look at it is, it's money in the bank. I made out well on pretty much every one, and would have to let them go real cheap to lose money.
Granted, I have also bought cheap amps. I have a $40 Vox Pathfinder 15R and a $100 '79 Marshall solid state Super Lead 100 combo.
I just really prefer valve amps, and always have my eyes open to anything that may come along.