I do not know what you are looking for, for it to be considered a good buy. What I can do is tell you why I felt it was a good buy. There are several reasons why I felt this was a good buy for me here are the following:
1. Compared to the Edge Pro and all the copies the construction of the Hapstone is fare superior, it being full metal construction.
2. It has several features which the Edge Pro is missing as well as the copies. For example the angle guide platform, the stone thickness compensation, the pull and push stoppers as well as the magnetic base. I'm sure I missed some others.
3. The versatility of the stone holder. By this I mean that you are not stuck with only using the Hapstone stones you can use stones from KME, Edge Pro and any aftermarket stones made for any of them.
These are the main reasons why I felt it was worth it especially the last one. Also food for thought buying good stones to free hand will be close to that cost and then there is a learning period where you need to get good enough to get a great edge.