fuck throwing loads of variables into the equation, just a round figure, only i've noticed people pay shitloads of reddies for something they sit on for a couple of hours a day.
for me, they fall into the "sort of thing you can always inherit or buy second hand" category, along with fridges, drawers and kitchen tables.
don't think i'd ever go above £200 anyway, even for a new one. lots of people seem quite happy to pay five, even ten times that for a leather one, etc. madness.