Things like this make me wonder why people don't use escrow when buying mining equipment. I guess because they don't know anybody trustworthy enough to facilitate it.
Nobody in their right mind would want to facilitate used mining gears, I declined dozen of requests because I know it will be very difficult to judge who is in the wrong.
As for your second statment, in most cases, you would test the gear for 10-15 mins and assume it's good, when they reach to the client and operate for 10-15 hours, shit starts, so it is very difficult to test a used gear, and then many of them break during shipping.
@OP, got any proof of Alex telling you anything about any payment?