There's an IBM silver badge M122 on eBay for $79 with free shipping currently. You'd have to buy a Soarer's Converter for it though, so another $40, but still not bad. F ATs have been going for around $180 in un-restored condition recently. F XTs are really cheap still, but that layout is so terrible it's hard to justify.
But really though, any buckling spring keyboard is going to be nice to type on so go for whatever makes the most sense for you.
nah, I'll pass.