I've heard mixed reviews on using 9-speed cranks with 10 speed drivetrains. 10 speed rings are narrower to fit a 10 speed chain. Some 9-speed chainrings have been know to stick to 10-speed chains. Be careful mixing and matching. There have been several threads on this lately, including one started by me.

The price jump you're seeing is due to the external bottom bracket craze, which most new cranks use. The idea is to make the crank stiffer and more efficient.

The idea is good, but the implementation so far hasn't been great. External BB's require heavier seals than standard ones, and thus have a lot of "seal drag". That reduces their efficiency. Many bikes they're putting them on also flex quite a bit near the bottom bracket, so making the crank spindle stiffer just forces the frame to flex more, whereas with standard BB's the crankset and frame would both flex.

Of course, the modern cranksets are substantially lighter because the spindle is hollow. In my case, moving to a modern crankset would save nearly half a pound...