I don't know if they'll ship to the US or not, but Princess Auto here in Canada can absolutely destroy those prices on motors. Here's their selection:
http://www.princessauto.com/farm/electrical/motors/list-all
I bought
my 240V 3HP compressor motor there a couple years ago on sale for $169. It was an unbeatable price. Even still at their regular price of $269 you're saving over $100 outright, not to mention that those prices are in Canadian dollars. It's an actual AC Century Smith motor, not some cheap Chinese knockoff. Even the guy at the local motor rewind shop told me to get anything small I needed from Princess Auto because it was impossible for him to compete, and that their motors were top-notch, just cheaper because of volume sold. That company supplies a huge number of the farmers and a significant amount of industry in at least Western Canada, so things like motors and hydraulic fittings are incredibly cheap there. Not to sound like an ad for the store, but I would be remiss to not mention it.
Phase converters or variable-frequency drives are useful if you have a few 3-phase tools and no 3-phase supply, but if you only have the one saw that needs it, IMO it would be a lot easier and probably cheaper to just switch the motor out.