It's not 3 extra magazines, it's 2 because the pistol came with 2 from the factory. I'd say about 800-825 shipped sounds right for everything. For what it's worth I tried to sell my AE P2000 5 months ago, NS, 3 magazines, great condition too. I was also the 2nd owner. I listed it on armslist in NC, and it took 2 months before a buyer offered to buy it for $600 - it was listed at $620. Then he decided an extra $20 in gas to drive here isn't worth it so I kept it since then - glad I did.
Also, the pistol is $840 new when in stock, $800 for .40 version. Night sights are $80, $37 per magazine, prices are from topgunsupply and shipping is $10 for NS and magazines combined. Unless substantial, like 6+ magazines, most people won't add much value to extras. You can probably get a little bit more out of it if you sell the two extra magazines and nights sights separately, just don't try to sell them for new prices if it's no longer sealed in factory packaging. It's used, the value dropped at least 10% when that first nonfactory round left the barrel. Even if it wasn't fired except for the factory test, then you will still have a very hard time selling it for the price as new because most would rather just get it from a dealer and be sure it's new.
I'd say keep it, I'm glad I kept mine though I might still have to get rid of it in the future when I anticipate to move to NY (likely).
Good luck with whatever you decide.