I'll respond by telling a story. A few years ago, I sold a 7-site project to the same end user. The total sale was close to $4M. There had been some "optimization" done at about that time, which basically meant getting rid of junior project managers, lead technicians, administrative persons, and so on. For the first six months or so, the project manager didn't show up to a single project meeting. I showed up to all of them. I directed subcontractors, coordinated with other trades, personally watched fiber being tested, and so on. I had no authority to do any of this, but I did it anyhow, because it needed to be done. When there was something I couldn't get done "unofficially," I'd walk into the project manager's office, and tell him what I needed, or deal with the admin, or whomever I needed something from. I felt like I deserved an honorary PMP certification for doing nothing officially, but getting it all done. The project rolled along fantastically, with me directing subcontractors and interfacing with the end user and other contract mechanisms, holding meetings, making sure everything went well. About the six month mark, the project manager showed up to a project meeting, without a notebook (I won't go on a diatribe as much as I'd like). The projects were expected to take 3-9 months to complete, depending on the site. The smaller sites were complete. I went to work for a different company. From what I've heard, talking to people still at the company, about three years after the projects began, the two large sites (accounting for about $1.7M) were not complete, and the company had basically walked off the site and left quite a bit of work undone. Everything was going smooth when I was there project managing things as a salesperson. Apparently they were not after I left.
I was paid on "expected profit." The way that works is that I put together a booking package, which includes all parts and pieces, the basic project plan, and so on. I ended up doing MS project schedules and other things after that, but the basics are parts and pieces, setting up turnover, and you're "supposed" to move on at that point and go sell other things. Based on this package, the project manager signs off saying that they agree that the project makes sense as presented. They're supposed to ask questions or concerns, do engineering with techs, VE everything, and so on.
The profit margins were good. I went to grad school for IT management. Everything was straight.
The job tanked, from what I hear. Not while I was there but after I left.
Word to the wise: Sending a tech to a job that is 1/4 of your entire branch's yearly quota for an hour, then calling them to do a service call on a convenience store is not a good idea.
To the original point, I believe sales persons should be paid on reasonable margins, and that the installation management team should have the ability to have a dialogue on this before accepting it. When the job is "booked," it can be a temporary thing, depending on your processes and systems, but within the first couple weeks after the PM has time to review, the costs should be normalized. The PM should agree to the normalization, as should the sales person and sales engineer (if they exist), and the GM or Director of PM (Or similar position) should review and sign off on the normalization.
You can hire a cat to manage a project, but that may not be the best idea. All key stakeholders internal to the company should agree that it will cost X amount of dollars (plus or minus 3%) to do the job. After that, it's on the PM and their boss to make sure the job is done. While I did a lot of things that weren't my job, that shouldn't be the norm.
Sales commission should be based on EXPECTED profits based on reasonable management, not actual profits. If you give a project manager, in the booking, a "whatever you need" fund for unexpected things, that is quite substantial, the salesperson shouldn't be punished if the project is poorly managed.
Related note: I've been a salesperson, sales engineer, and project manager. None of those categories should be punished when another category doesn't do their job.