They're not the cheapest either (in the Uk anyway - not too bad in the US) but I agree, having them screwed to the bars is brilliant! Makes life a lot easier, it sits firmly wherever you want it in the cage and whatever height you want it
If it's for a Syrian the 29cm Karlie Wonderland wheel isn't that cheap any more as Zooplus seem to have stopped stocking it and it's expensive on Amazon. That was nice and quiet too, but they might need a light sanding (there have been issues with splinters) and painting with plastikote.