I paid about $115~120 for my MP01. Never got the Hasbro version, so I don't remember how much it sold for here.
Good or not, metal is a more expensive material so it would justify a higher price compared to using more plastic. It's similar to how some people feel that more recent TF toys (e.g. TFPRiD, DotM, TFP) feel like less value for money because these toys are smaller and lighter weight than previous figures -- e.g. Generations Wheeljack vs TFPRiD Deluxe Wheeljack. I don't have any objection against plastic per se. I just don't like paying more (or the same) for a plastic toy if a metal toy can be the same price; e.g. when Alternators first came out here, they sold for about $55. For about the same price (4980JPY/$53) I could get a die-cast metal Binaltech... why not just get the Binaltech? The colours tended to look nicer on die cast metal, and Takara just put more effort in with the toys anyway.
Having said that, I agree that $150 is still a good price for Hasbro MP10. It's a lot better than paying $244 (23100JPY) for it if you got the TakTOM version (even if it has much nicer colours).
MP04 has an Energon Axe and Matrix too, but no Roller or Spike. IMO the MP10 trailer is nicer than MP04's. Sure it's smaller, but I find that it's better designed -- looks better and more fun to play with. It's also more similar to the original G1 trailer with the extra sculpted features and places for Spike to sit in.