The beauty of OSS is that there are plenty of people willing to play ball, and they all can. So, in your hypothetical, one project maintainer is unwilling to quote you a price. Big whoop. Approach a company that professionally offers support for this project. Send a general RFQ to the appropriate mailing list and see who bites. There is an entire market worth of solutions.
Your hypothetical seems to be stuck in a vendor-client mode of thinking, with the maintainers just vendors-by-another-name, the implication being that they wholly control the ability to modify the software in question. If that were the case, 'no' would admittedly be a deeply unprofessional answer, and your conclusion would make sense. However, maintainers are not vendors. They're arbiters of what the public project is, but they have no control over what you do with the project in the confines of your domain. Acceptance of a patch into the public project is not a precondition for using it.
Your hypothetical seems to be stuck in a vendor-client mode of thinking, with the maintainers just vendors-by-another-name, the implication being that they wholly control the ability to modify the software in question. If that were the case, 'no' would admittedly be a deeply unprofessional answer, and your conclusion would make sense. However, maintainers are not vendors. They're arbiters of what the public project is, but they have no control over what you do with the project in the confines of your domain. Acceptance of a patch into the public project is not a precondition for using it.