Small business BIG non-refundable deposit

[lake3x]

I have a small custom golf cart shop. We took an order for 3 very custom golf carts. Our policy is to take a NON-REFUNDABLE deposit for 60% of the total order. In this case the total order was over $55,000. Deposit of $33,000 paid by customer on AMEX (I know, bad decision). Custom carts take awhile to build, and it took a little longer than anticipated, but still done by their deadline. 1 week before deadline, I contacted them about paying the balance. They filed a dispute with AMEX to get the entire deposit back, saying they are unsatisfied, after they gave me a deadline and I beat it. So now I'm stuck with 3 custom built carts, and fighting with AMEX to keep the deposit. I'm sending all the emails etc stating when the carts were to be finished etc. Do I have any chance of winning the dispute? How can people get away with doing this? This could very well put me out of business if I have to come up with $33,000 to give them back, after having about $50,000 into these CUSTOM carts.

You could very well prevail in court.

Even the threat of a suit may cause them to compromise.

They were not really damaged by some delay you wold have to argue