A company I used to work for had an interesting solution to this.
There was an internal market, and all services used had to be paid for. Sales people could keep everything after paying the company a cut and all the costs of delivering what they promised the client.
So if they over promised to get a sale, it all came out of their personal profit. Seemed to work quite well.
I'm not clear on the details. It was over 30 years ago and I wasn't a salesman. I was busy automating their warehouse systems, but I'd see the brand new Porsches pulling into the car park!
The entire company was structured as a set of internal markets though. Never seen anyone else do this.
There was an internal market, and all services used had to be paid for. Sales people could keep everything after paying the company a cut and all the costs of delivering what they promised the client.
So if they over promised to get a sale, it all came out of their personal profit. Seemed to work quite well.