I think it's unrealistic to expect 2/3 of your corporate users to pitch in $6k to support one of the many OSS projects they use. Not because it's trivial to build or anything, but expecting those kinds of rates is just setting yourself up for failure. If you really want money from them, figure out what it is they want from your library, maybe they're perfectly happy with how it is, maybe the work you're proposing is…
> I think it's unrealistic to expect 2/3 of your corporate users I didn't phrase myself with sufficient clarity (2000 chars and all): the project itself has an enormous footprint. It is essentially the ORM/SQL-generator of choice in the Perl5 ecosystem. What I meant by "I know of (and contacted) at least 34 companies" was the corporate users whose senior engineers and/or CTOs I know personally .
For example, see https://www.kickstarter.com/projects/tomchristie/django-rest... which is widely used Python library. In that campaign, it is easy to see how much time the author would be able to continue to commit to the project at various funding levels, and specific features they will implement.
Even if the commitment at a certain level is just being able to provide on-going bug fixes, this shows the value to the company rather than backing being presented as a thank-you for previous work.