Designers and devs and makers too busy doing their jobs to bother with your arcane requirements and need to do an 'apples-to-apples' comparison on every bid, respond to hundred-page RFPs in nitnoid detail, buy you drinks so they can suss out why you don't actually know your own requirements, navigate your own effed up procurement process, your politics, your internal power struggles, and your primadonna self-belief that you are special.
Buyers are in the power position for sure; you write the checks!
But just know that there's a whole layer of people out there who end up in sales who have to clench their teeth and endure the bullshit of dozens of companies in their portfolio – in the same way you might feel like you have to endure theirs.
Be a qualified lead. Show you have your shit together, and then yeah we can start bringing sales engineers and devs and designers into the conversation so you're not wasting their time.
If you want an easy procurement process and no regrets, follow best practices: come to the table with your internal and external research done, with a clear list of requirements, an executive sponsor with actual decision-making power. Understand that if you change your requirements midstream the budget will change. Pad your budget so I don't have to pad my estimate.
Sales guys can be douchey for sure, but that doesn't mean they're trying to scam you. Their incentives are more closely aligned with yours than anyone else's.