Jira with Greenhopper is almost free: $20 for up to 10 users. It beats the pants off of any open source solution. For us it won out over Fogbugz in the trials.

Jira with Greenhopper is almost free: $20 for up to 10 users. It beats the pants off of any open source solution. For us it won out over Fogbugz in the trials. When we pass 10 users (there's currently 5 of us), we'll pay their regular price. Anecdotal evidence against the assertion that people reading this will never give FogCreek/Atlassian a dollar: we will.