Hire a department full of persuasive people. Expect to get persuasion. On top of which, subverting an organization's decision making processes and channels is a core competency of good sales departments. A two-edged sword if there ever was.
I assume they're gesturing at commissions? Salespeople are usually paid based on a percentage of the deals they close, incentivizing them to promise more to clients in a given timeframe than the eng team can realistically deliver. Then sales usually leaves it to eng to readjust the client's expectations. That's the classic conflict between the departments.
I personally don't really mind this since at the end of the day the entire org exists to support sales, marketing, and retention. Within reason, if those groups say they need something to bring in revenue then they get it.
Yes of course, but if you don't do it right you might get the sales (and the sales people get their bonuses) but the retention will be abysmal. For example, a salesperson who promises features or deadlines without consulting the tech team about what's doable will cause unnecessary crunch, poor quality releases and angry customers.
