Once you're at this level, you're looking to get improvements of a fraction of a percentage. I don't know the specifics cause I'm not a pro shooter despite being American, but from other high level skill people I know, you hit a point where improvements basically plateau and you have to resort to increasingly niche products to obtain non skill improvements. If you want proof of that, check out calligraphy and fountain pen communities. The amount of money some people spend on things I didn't know existed is wild.

(No bad judgement to those folks, I've gotten hard into map making and 3d printing lately, so I'm right behind you)