I wouldn't overthink this, it's mainly the psychology of the people who work in the bowels of big companies. They are used to having vendors kissing their ring,

I wouldn't overthink this, it's mainly the psychology of the people who work in the bowels of big companies. They are used to having vendors kissing their ring, and on some level they justify it by thinking it's because BigCo is such an awesome big company. So they take that posture with "vendors" who are random open source devs on the internet. But these people are usually the most cynical bastards you can imagine, and they really know it's all about the money. So, I'll echo the other suggestions, and recommend you send them a professionally-worded proposal. If they know can spend $X to get Y, (and Y kissing their booty) they'll drop the pretense and 'do business'.