As others have already mentioned, the upgrades are at least slightly different between different powers, relying on the force trees alone is insufficient.
I have a similar issue, but with the various upgrades of move (the strength one in particular).
All of the move upgrades are described with the "You can activate this multiple times" clause.
Assuming that all 4 strength upgrades are purchased, RAW one can:
1) use 1 fp to activate the base power
2) use 1 fp to increase the silhouette from 0 to 4, a second one fp to increase it to 8, and a third to bring it up to 12 (in the books the largest capital ships and stations are described as sil 10).
So, in theory, 4 fp to perform a short range move of an object of up to sil 12. With a bit of luck, a FR 2 would be enough to pull it off. With FR 3 and some range upgrades, things get even more extreme. Considering the applications of move we see in the movies, this should be impossible.
Our interpretation is that each upgrade can indeed be activated multiple times, but only once per object that is to be simultaneously moved. This makes move much less broken, as it would cap the sil at 4, which is the size of a typical YT freighter. Still a very impressive feat, but at the same time in line with the movies.