How do I pay?

Zero. Feedback, wants a cashier’s check? This deal has SCAM written all over it! 

kjohn1234 OP

Tell him you'll pay the Paypal fees on top of the $4000, if he doesn't do it then forget him, he's a scammer.

Cheers George 

This is a common scam, don’t do it!!

PayPal is not always protection.

IF there is an invoice for goods (i.e. specifically naming the speakers), then you have PayPal protection.

IF you just pay via PayPal, without an invoice, it is 'sending money to friends or family', with ZERO protection.
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Seller pays a fee to PayPal when selling goods. You can offer to pay the $4,000. plus the fee via invoice thru PayPal.

If seller still refuses, I would walk away.

Pass on the sale, other opportunities will come along.