Honestly, I don't actually get what their fee is even for with a membership fee and it being all online. It's just that for a lot of people, it's the only choice (i.e. both HGVC and Wyndham only use RCI as far as I can tell) and so you pay the fee if you want to use it. But it's got to be all profit at this point.
I started off thinking exactly what you do. And there certainly should be an element of truth to it. But I expect their costs may be higher than you think. For us informed users, it should entirely be an online system. But they still do a world of business calling people up on the phone to book exchanges. It has to be a significant part of their costs. DRI (before HGVC bought them) built their own all digital exchange (DeX) where DRI created the consumer facing exchange and it ran on RCI on the back side of the portal. I believe it charges $149 per exchange, and RCI and presumably DRI are not losing money on that. So just digitizing it that much could reduce exchange fees to $149.
But lack of competition also keeps them fat and lazy instead of innovating to save costs. Every single time I book an exchange on RCI or set up an OGS, it asks me to opt in or opt out of their text messaging service. I always get a text confirming I have opted in. FOR YEARS, I HAVE NEVER GOTTEN ANY FURTHER TEXT MESSAGE ... INCLUDING ONE TELLING ME I HAVE A MATCH. But if you don't opt out of phone calls, they WILL MOST CERTAINLY CALL YOU ON THE PHONE TO GET YOU TO MATCH OR MAKE OTHER PLANS.
Why in the world have they half-implemented (but not completed) a texting system that would save them who knows how much on phone calls? Answer: there is no competition to have affordable costs or build a more efficient system.
I will also acknowledge their exchange fee had been flat for a few years before COVID. Dring COVID, they were running a real backlog on processing cancellations and refunds. It appeared to be staff intensive on the backend. They have been jacking fees up constantly since that started.
What I wish they would offer is something like a more expensive platinum level that came with something like free exchanges or unlimited $50 exchanges.