I don't think anyone would fault a vendor for charging a startup that built a billion dollar valuation off of their tech stack more money. In fact, I'd question

I don't think anyone would fault a vendor for charging a startup that built a billion dollar valuation off of their tech stack more money. In fact, I'd question the business acumen of a vendor who didn't do that. Of course, most people know better than to use someone else's technology to build their business.