Never try to justify your pricing. The moment you go down that rabbit hole, there is no coming back. You will give 1 reason and they will continue to challenge it.

Best way is to just say "It is company policy and I am afraid we cannot work around that. I am happy to discuss alternatives" and go from there.

I find that being a solopreneur (or just as CEO of a small startup), it's hard to invoke "company policy". You can say your board won't go for XYZ, but if your customer knows you own most of the company, that wouldn't fly either.

Tips?

Good point. You could replace company policy with "I do offer Escrow option with a customized/enterprise plan at $x/Year with a minimum contract to compensate for the additional overhead, cost and risks that comes with setting it all up"

Then, stick to it and don't try to justify it too much.

"Experience for previous clients shows that this is the best solution for everyone involved."

Risk, administrative burden.