Why is it purple? Has it got some dmg mods?
For sure it didn't drop like that... so either you didnt specify the dmg mod or you overrid a previous upgrade.
I usually sell req. 8 clean for 5k, that one is worth more just because of the upgrades... maybe 30-35k...
It would be bad if you spent 50k on upgrades for a bow that doesn't have a damage mod built in. It's worth putting perfect upgrades on a weapon you are going to sell only if that weapon is really perfect= low req and a +15>50 or +15 ench etc. or if you plan to use it yourself.
The thing is if you upgrade a weapon which is not perfect and want to resell it you will never get the money back you spent on ups.
Hope it helps