Early returns on the Ruger SR-22 are that it's a pretty cheap pistol that seems to run very well and not finicky on ammo.
My GSG 1911-22 ran about $319 when I bought it and it's performance has simply blown me away. Over 3,700 rounds through this pistol since April and it's been as reliable as you might ever ask a semi-automatic rimfire .22 pistol to be.
If you can find a used Browning Buck Mark at that price point, you can pretty much bank on it being a very reliable performer. I'm not sure what they go for new.
Knowing what I know & have seen from the Ruger Mark III, I wouldn't take on at any price other than nutbar (to flip it), I'd spend more money on a lightly used Mark II than I'd ever consider on a Mark III. But then again, if your desire is a .22 pistol for low dollars that works well, don't discount a well worn and unloved Ruger Mark I if you find one for low bucks. They have made zillions of them, so you can find them cheap quite often, and those run forever, too. My buddy has one from 1982 that he picked up years ago from a co-worker and I found out MUCH later that it has a barrel bulge -- and the dang thing still runs 100% of the time and it's accurate, also.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.