Let's say you actually sent somebody $5000... and if they just ran away with it you would reverse the payment. Even if they bought you the 4500 in BTC and sent it to you, what's stopping you from reversing the payment anyway?
And if that's not the case why would you trust a stranger with an irreversible payment?
Let alone the fact that you can buy bitcoin within the Square app, nothing about this deal makes sense.
Depends on where you go. I found one that was buying LTC for slightly less than 4% the other day. 8-10% is pretty standard. So a 10% (or 11%) commission is actually more money for a much stronger chance of getting ripped off.