I'm not an expert on value, but that seems incredibly high. Its also not a particularly awesome selection of games in the first place. I mean, if you have a SGX, what are you going to do with a regular PCE? Half those games are worth about $5 or less, and many of them are pretty so-so. After spending $650 you should damned well be able to play CDs!
If you have the bread, the best way to get into PCE is to buy a Duo R, and buy the best low priced games one at a time. Ask here, and people will gladly tell you the best cheap PC Engine games. Going this route you could easily build a WAY better collection than this for $650.