A link from a high value site might be worth hundreds of times that of one from a low value site.
The raw count of links to your website can be an indicator of how your SEO plans are progressing, but remember that the quality of each inbound link has an enormous influence on its value.
A link from the home page of IBM, with its PageRank of 9 and probably a very TrustRank, might represent enough new inbound links to last you a year.
One high quality link can be worth several hundred mediocre quality links.
Still, everything adds up. Links of lesser value might not be as important from a PageRank point of view, but some such "lower value" inbound links can offer a different reward: they might drive visitors to your website because people click them. Inbound links have three possible functions (1) increasing your PageRank, (2) driving visitors to your site via click-through, and (3) educating people about your existence when they see the link, even if they do not click it.