I don't know a lot about .io so take this as an opinion and nothing more than that.
I think 10% of the .com is too high at this moment. I see the .net normally at 10% of .com. While .io has proven to be a strong alternative, it is mainly focussed on the tech niche.
I would say $1500 would be a good asking price if you keep room for negotiation. I would personally be happy to fetch $750 for a .io name at this point. You could also hold on to the name and wait for inbound requests and/or .io establishing itself beyond the tech market.