gj not understanding very roughtly defined time, as well as meaning of "over 9000"....
your math cotains several errors, too
1) one screeen have 20 items, not 25
2) 10 seconds per screen (which should be close to truth) would be mindlessly sacrifiging every single item. Except nobody sane does that - you need to leave several of every item for future mech consttuction, well, unless you are not planning to use ANY common or rare items. So, need to check how much of that trash you still have. Consider this in calculations, too.
3) one item is not 150 power, unless its level 30 non-module. Instead, try counting all game level 15-30 items and their average power, then insert THAT npower value here.
on the other hand, you are right about very fact of large amount of not used power. But it will take terrifying amount of monotonous, boring work to put that power into items - which is not appreciated from a game (aka something where fun is experted, not boring work). What OP would probably use is measures of dispatching of unneeded items more quickly