Sir, that is nothing new.
I have been gambling at primedice for a pretty long time, i can say i have seen many thing happening on chat.

Staggo is a well-known scammer, as you said everyone should stay away of him.
Dont trade with him, dont send him anything, there is very high chance that he will try to rip you off.

I have a friend which was scammed by him too,I'll talk to him to show his proofs over here.

Im sorry for your loss Earthman, I know it was tough for you to made.
That will be a lesson to you, to always make a screenshot of every PM if it is about trading/giving.