We still have seen no pictures of this horn. I agree $525 sounds reasonable, but it might be even more or less reasonable depending on the severity of those dents you mentioned.
I'm of the opinion that if a tech is meticulous enough in an overhaul, a student instrument almost always can be brought to better condition than when the horn was new. Even new professional instruments can have a few issues. It's possible that you could get another one as mentioned here and pay a lower repair bill and come out spending less, but not a guarantee. It also depends on the pads. I would charge around $350 for an alto overhaul (not including significant dents) with standard pads (I'm very new to the trade mind you, but saxes are what I know most about), but they don't all cost the same. Curt, who commented above there (MusicMedic) has some spiffy kangaroo leather pads, which cost more, but justly so, so it would be like $40 more. That's a fluctuation without even seeing it...so it really depends. Curt's overhaul would probably be more, but he's got someone working on every key of your instrument with 10 years of experience and could probably change the keys to slide keys and put "series II" on the bell and fool a few people hehe.
Whatever you decide, best of luck with the horn.