Hi, Sorry to say, but for me domain has only reg fee value. Here are the reasons
1. In 2010 there was a buyout of L-L-L.com domains. That lead to the sale of $2050 sale of S-E-O.com. If you try to sell it today, you will not get that money. Probably $200 - $300 IMHO.
2. Even most of the registrars try to show that the .co is the next big thing after .com, it is not. it is still a ccTLD. On landrush there were some good .co sales and recent past they are declining. .CO is a good extension, but not with hyphens.
3. The person trying to sell SEO.CO is also a domainer & he price like a domainer. We always think my domain is worth xxx+ or something. But the actual value of it is what the buyer like to pay. The the price we like to list.