I would have probably paid at most ~$5k per dose, both for myself and close people in more high risk groups. This is based on a gut estimate, not on some calculations.
But I have a better answer. I made it having about 10 close people in mind. I've spent smth like 2-4 full-time working weeks on research research and sourcing the ingredients plus <$1.5k (this is worth much less than my time). This ended up a marginal call, considering that I finished it quite late, but it is still somewhat justified on the basis of learning a lot of things and having an interesting experience.
I estimate its safety as very safe (roughly as safe as the commercial ones) and its expected efficiency as ~30% (90% if it ends up immunogenic enough). The expected efficiency is so low, because peptide vaccines have low immunogenicity. Thinking about it now, adding an adjuvant like alum would be a good idea.