This doesn't really need to adjust to the price of Steem because the idea is to limit the number of content elements which can be profitably rewarded by milkers (to in turn limit the amount of effort required by altruistic volunteer abuse fighters). That's a function of the size of the reward pool which is a set amount of STEEM. The price doesn't change that.

To put rough numbers on this the reward pool is about 50k STEEM per day. If the cutoff is 16 STEEM that means there can't be more than 3000 content items which are milking candidates (and probably less since rewards will be somewhat concentrated, not spread out evenly on 3000 comments). That's a number (or really a range) that is likely feasible for abuse fighters to keep on top of. 300k would not be.