They get paid a portion of the proceeds of a sale (or raise if you decide not to sell and raise money instead). The bill was almost certainly from his lawyers. I went through a failed M&A process and we were left with a 90K bill for it.
> They get paid a portion of the proceeds of a sale
This is true for most M&A. But with KPMG, last I saw, they charge a retainer that must be re-upped from time to time. (The joke was that's what you get when you hire accountants as bankers.)
Having been through a similar process with KPMG (that ended similarly), I can confirm that they operated on a retainer basis and it did need to be re-upped from time to time. The vast majority of their remuneration was a success fee though. This is pretty standard for the industry.
Just to cite one example, he says he was billed by the lawyers arguing whether he was legally considered a "sophisticated investor". I imagine there's not a single party in this process that works for free or on a commission. There's a lot of work done even when it doesn't result in a sale.
Where did the bill come from? Did he get billed by the prospective buying company for not purchasing him?