You say "add memcached" like it's easy to do on 10 year old wiki software. TVT is running a highly custom Pmwiki install, with no upstream updates in a long time. The something wrong isn't the hosting costs, so much as the sole developer/owner/admin running the site.
I'll also note that the forums make up most of the traffic of the site, and that's the one place you can turn off adverts for free. The wiki supports the core product, which is apparently the forums.
If I was an admin there, I'd probably have made upgrading to some new software (that actually supports special characters etc. in titles, doesn't drop edit history off the end of the page into /dev/null, doesn't have the weirdest way of creating links I've seen, etc.) a key priority.
I'll also note that the forums make up most of the traffic of the site, and that's the one place you can turn off adverts for free. The wiki supports the core product, which is apparently the forums.