Spend as much as you like on one, innit.
Dunno whether Theo’s annoyingly monikered @1101010 incarnation was joking, but I’ve got two IKEA Klippans that have served me very well and lasted me best parts of a decade and a half. £150 each. Bish bash bosh. Wish they did a corner Klippan.
And I couldn’t disagree more with @GEOFF 's claim that…
It’s rare to find a sofa that’s desperately uncomfortable
Many, many sofas are, indeed, very uncomfortable. Many more are also ugly as feck, obv.
@hip_young_gunslinger 's sof goes well with his milking chair, I suppose. There’s that.