Well, aside from this specific situation, ultimately one party must trust the other party. Who better deserves the trust, the party with long established reputation or the party new to the scene?LOL. If he is so untrustworthy. I hope someone else buys it.
On another note, it occurred to me that little was said about the product. Is it working? One would assume that it should be but it wasn't explicitly stated. Has the OP successfully paired it with a Perdix AI? Or any other DC? When was it purchased? Was it purchased new or used? Why is it being sold? Is it returnable? Details like that also play big in assessing trust. $150 for a working transmitter is a very good deal but not for a paperweight.