Sounds like you have a decent cost effective solution. Doing it yourself with Windows Enterprise server, some Multitech modem cards... Well, the modem cards will cost your yearly fee alone.
Think of it: rack mount modem banks... ARRRRRRGGGGHHHH!!!! And the upgrade was from rack mount to 4 or 8 modem PCI cards (I forget if it was 4 PCI cards with 4 modems on each or if it was 4 cards with 8 modems each... Phone line wire nightmare to a server! Esp. getting it all to fit in the server cable guide.)
We had all our inbound fax lines going to email from the Windows Enterprise server (Enterprise Server is required to support this many, like 24, modems) via Multitech modem banks and then the daily price changes faxes going out. I had to be careful not to use all 24 phone lines at once on the company T1 while faxing out. We had fax stations that would fax out only. This got rid of a bunch of expensive personal fax machines and phone lines. And this was 10+ years ago. Modern equilalant is Multitech FaxFinder offering.
Yes, some places don't have email and depend on faxes for price changes, signed contracts, etc.