Domain age as a price determinant on an expired domain? Absolutely not. I have talked about this on this forum at least a few dozen times, yet people still repeat the same wrong info over and over again.
Domain losing power after it drops? Again, absolutely not true. This would completely break the internet when you think about it for a minute. Also, nobody would pay anything for expired domains that do not work. Use your heads here please.
Did you know that auction domains are also mostly dropped? With some exceptions of course, like Godaddy, who list them on auction already during grace period. Other big auctions like Namejet, Snapnames, Dropcatch are all catching the domains after they drop. Another exception is ofc Flippa and similar who sell live sites.
So again, people just parroting same wrong crap all over again, because they "read it somewhere" and they can't be bothered to actually get a first hand experience. So anyways...
Regarding the OP:
1. Strength - Considering we are on a SEO forum, the primary determinant for us is the domain power. Rule of thumb as a quick filter is the number of referring domains. The main factor is of course power of backlinks that has to be hand checked.
2. Niche - Niche of the domain does a lot. Big health niche domains go for x10 and more as compared to other niches. I've seen dozens of times domains that would normally go for $2K, go for $15K+, seen even some at $40K+ just because they are in health niche.
People used to post CPA products on them for quick churn and burn. That was to a huge extent killed by the May update, but still works to some degree.
3. Cleanliness - Nobody will pay too much for a spammed domain. Most people however couldn't recognize previously abused domain if their live depended on it.
4. Brandability - This plays a fairly huge role if people are going after the domain for money site purposes. It can easily double or triple the price. (Again, I am not talking about LLL LLLL domains here).