Forum Moderators: DixonJones
AFAIK most of those work by having tiered programs - track last 100 visitors for free, unlimited visitors for X/month. The problem of course is that for anything but the lowest-traffic site, 100 visitors is not even a day's worth of traffic.
Of course, if you are looking at stats based on your log files, there are free and open sources packages to crunch the numbers, but that's quite a different data set than what google offers.