This domain is reserved by the registry.
Anyways, domains like this are hard to appraise.
Anywhere from $45k minimum to $150k
Would list on Squadhelp and Sedo or use a broker like Grit.
Given it is reserved, the registiry (if released) would likely want to see it put to good use.
Downside with that domain was google chrome/brave didn't recognize it as a domain and redirected it as a google search after inputting it into the URL bar. My personal business uses a .co and I've never had that happen before. Unsure if that is because web.co isn't a website.