Much of my contributions to open source, and what I've made available in terms of projects, is quite literally just "this functionality wasn't available", or "this was poor UX", and offering my solution to whoever wants to incorporate it into their stack, or into the main project.
It's like sharing construction/tool tips while working in a shop or maker space.
Does my time have cost? Sure, but I'm there because I enjoy it. And the nifty thing about software is that it's basically free to distribute.
I'll add - I don't provide any support or feedback for my software at all to users. I don't find that fun - so I don't do it.
Physical items that have per item costs? Pay what the item costs.
Digital items that have no per item costs? Pay what the item costs (nothing).
Your time? If you want to be paid, start a commercial venture (aka - a company that charges). If you're doing it because you like it? Charge what you'd like - in my case nothing.
Cost: the inputs of time/treasure to produce something
Price: the value sought for something on the market to compensate its creator for its cost.
Anyway he's saying that free software should have a price, which is tough because customary definitions of the 'something' being priced/sold are inadequate.
'things' we have tried to price when trying to offset the costs of OSS:
1. support
2. good vibes from the developers
3. CD-ROMs
4. 'premium' features
5. ??? (add yours)