I agree that achiever is great, but I felt that topscore was the best representation of the actual DAT test difficulty and conditions. I think it is worth 50 bucks considering the monumental cost of applying, interviewing, and dental school
Although I don't have experience with Achiever, I'd say for the PAT and the sciences, Topscore was a very good representation of the real DAT. I scored exactly the same on the PAT and about 1-2 points higher on all the science on the real DAT