Your comparing a top of the line 4s with a middle of the road 2s. Lets get a little closer:

Your Saito .72 –
470 grams – 1.2hp - $229

Rossi .45 – (side exhaust sport, not the Q or rear exhaust)
430 grams – 2.1hp - $129

Like I said, (roughly) half the weight ( to hp) half the price. And we haven’t even started talking about the pylon engines or pipes. Yea, you could also bring up torque curve and fuel efficiency but I could match that with cost and durability. Yes I am a little partial. I used to be big into Kart racing and built and tuned my own engines. We were of the opinion the 4 strokes were for old men, kids and lawn mowers. Other than scale acft I can’t think of a use for them. I guess the pattern guys are using them now. I don’t know anything about pattern. They’re probably not worried about weight or speed and that big disk is good for slowing things down. Getting rid of that pipe down the fues is a plus also. To each his own.