I always found that the best sprockets were OEM when I had my 750F2 and 550s. The quality of some pattern stuff was not that good.
As for chains, the 630 size on my 750F2 was quite large & so the prices of new chains reflected this. One chain that I regret buying was one thrown together by Regina. Although an 'O' ring chain, it stretched so much within 1800 miles that I had to replace it. In the end I bought one made by Izumi which was OEM for GS100s at the time. This was on the bike until the big smash.