It’s called “skip lagging”. The airline can possibly try to collect money and if you do it often, ban you from flying with them.

https://www.npr.org/2023/08/23/1194998452/skiplagging-airfar...

The reason is happens is that take for instance ATL (former home). ATL is a Delta hub and has direct flights to a lot of places that other airlines don’t. Between people preferring direct flights and the lack of competition, they can charge more.

But flying out of MCO with a layover in ATl, they lose the non stop flight advantage and they have to compete with other airlines.

Also ATL sees a lot more price insensitive business travelers than MCO. Businesses aren’t going to force their salespeople and consultants on one of the low cost carriers.