Exacts are usually the most important figure - Exacts determine how many visitors one could make with this site if they purchased the domain name. Trends are also very important (Is the market population (searchers) going down over time)?, so together the two form a basic system:
Working out how many visitors you could get from search engine results for the primary keyword
Working out how many visitors you could get from search engine results for the primary keyword in a month's time, 6 months time, a year.
For example, something with high exacts (Like - and I haven't checked the real exacts - "CD shop Devon" might have 3,000 Exacts today, but if last month it had 3,300, and 6 months ago it had 4,800, this shows that the market is rapidly shrinking, thus rendering this domain name much less profitable for long term profit or selling of (no one wants the low-exacts and dead market that this domain name will be with), so this domain name might sell cheap (£200?).
Lot's of domain names related to technology, services, computer & electrical products are more highly priced then your "average domain name" on exacts. That's because something like "Deleteaccount.co.uk" might have roughly 60,000 exacts in it's field now (things like "delete facebook account"), but it shows high promise for this to continually increase. As more people are using services with accounts, more will need to delete these accounts, and more population also causes more accounts, with more need to delete these accounts. So very likely the next month the exacts for it's field will be 62,000 - And then 64,200 - and then 66,500, and so on.
In order to compare to the devon domain name I'm going to pretend that delete account has only 10% of the exacts detailed above, but also dead exact searchs
A domain name increasing by 3-4% per month @ 6,000 Exact Searchs will often be valued very highly (£4,000)
A domain name decreasing by 10-12% per month(and this figure keeps getting bigger - in a year it might be 50%) @ 3,000 Exact Searchs will be valued very lowly (£200).
Figures are estimates, but they are my realistic ones, in other words, yes exacts are important, but more importantly is where they are going. The decreasing devon domain name delivers half the searchs of the other one at the moment, but (@ £200 x 2 = £400) will only fetch 10% of the price. That's how much difference trends can make.
You might argue that the devon domain name is more targeted costumers / easier to get money from, so just adjust search exacts accordingly.
Exacts can be misleading too. For example, the domain name
www.deleteaccount.co.uk only has about 600 UK exacts - mostly clueless people who expect some google result to know what account their talking about - but the number of exacts with phrases like "delete facebook account, delete twitter account, delete hotmail account", tally up to around 60,000. There is NO better domain name for those searchs without copyright infringing, so you could say (and I generally consider these exact in cases like these -) that the domain name has 60,000 exacts.
Make sure before purchasing a domain name you check out terms which include the domains keywords plus one other copyright word (that can't be used in the domain name" - like "Dresses.co.uk" & "Dresses dressmakehere". These little golden nuggets can be just a useful & achievable as normal exacts. If you ever sell a domain name like this, then make sure you point that out.
Exacts, however, are usually used as a quick judgment. That's why sales threads often include the domain name + local exacts (for .co.uk) - it gives you a quick look at the current achievable market.