The price difference between HobbyPartz and HobbyKing are due to HobbyPartz being in the USA and HobbyKing being in Hong Kong. The price increase is due to shipping and import taxes. Actually here in the USA, HobbyPartz winds up being a little cheaper to buy from as the shipping costs from Hong Kong to the USA raise the cost to more than what HobbyPartz sells them for. HobbyPartz had a free shipping offer on everything for a long time too.
Now the HobbyKing version ASP engines do have the ASP logo on the crankcase, whereas the HobbyPartz ones have a blank side. The HobbyKing versions come in a nicer looking ASP logo box and have a small instruction sheet, whereas the HobbyPartz ASP engines come in a plain white box and no instructions.