The resale value of domains has fallen through the floor, especially .io. I assume because of the huge number of TLDs now available and the familiarity of them by the general populace. I tried selling, then auctioning my domain rb.io for months and finally accepted an offer of $2k. A few years ago a two letter domain like that would have gotten 5 to 10 times as much. I know because I was an early adopter of .io domains and sold karma, clever, flip, xs and maven for $8k to $10k over the years. I was shocked at the disinterest I got in my last one.