The potential customer is not in your market segment.
In part because you cannot deliver what the potential customer wants. In part because you don't want to change your business in order to deliver it.
So your choice is basically, forego the sale or sell something you can't deliver. Because your product does not meet their requirements.
There are two options. Be honest with the potential customer about your limitations. Or sell them reliability that you cannot reliably deliver.
Ok there is a third option.
There are 168 hours in a week. That's 4.2 FTE's. A Silicon Valley engineer salary of $120k is $10k/month/engineer. 50% overhead makes that $15k/month/engineer. 33% profit makes that $20k/month/engineer.
Doing it right is $88k per month. Or just north of a million dollars a year. If you cover some of the on call, then you can offer a discount down to $1,000,000/year for a year prepaid. Good luck.