Hi
typical USA/English version is 'humor'
and as such, would lose traffic to humor.io or even humour.com which is developed.
so best bet is UK and maybe Canada
and...because of those issues and regional usage, that reduces appeal.
along with it being .io - and not .com or co.uk
still, maybe $$$, perhaps more if you find somebody facinated with .io in particular.... and they can overlook the spelling issue.
imo....