Wow. Back in the day Futurama was the cheap and crappy end of gear. First electric I played was a 1-pickup Futurama, non-intonatable, ali pickguard, fed back like hell. It belonged to our bassist's brother. He also had a 5W Futurama practice amp that didn't cope too well with bass and guitar simultaneously.
The price of old Selmers has fairly shot up, but if I was in the market for a vintage valve amp I'd probably want it to come in snakeskin and have a magic eye that flashed in time to the tremolo rate. $700 for that teeny wee one seems a bit much, but they're obviously a fair bit rarer on the other side of the pond. I'd say hold out for a Zodiac or a Thunderbird.