I switched to Droid with about half of my AT&T iPhone contract left, so I knew I'd have to pay a cancelation fee. I had a iPhone 3G (not S), so I didn't think I could get much for it. Fortunately, I actually MADE money by switching. Here's my breakdown:
Droid (Best Buy) - $200
Activation Fee - $35
AT&T Cancelation - $100
Total Cost: $335
Ebay sale of iPhone: $389
Net gain for me: $54
Now I will mention that I did do 3 auctions on ebay for my phone, since the first two were "purchased" by Nigerian scammers (BE CAREFUL!), and I was super nervous when I actually did ship my old iPhone to the winner, but in the end, it was completely worth it, and I almost completely covered my first Verizon bill in addition to covering the switching cost.
Droid (Best Buy) - $200
Activation Fee - $35
AT&T Cancelation - $100
Total Cost: $335
Ebay sale of iPhone: $389
Net gain for me: $54
Now I will mention that I did do 3 auctions on ebay for my phone, since the first two were "purchased" by Nigerian scammers (BE CAREFUL!), and I was super nervous when I actually did ship my old iPhone to the winner, but in the end, it was completely worth it, and I almost completely covered my first Verizon bill in addition to covering the switching cost.