What’s left out is accounting of the time the paid tool wastes. Ten seconds here, a minute there, two seconds another place. If the open source solution is in fact the more productive tool (nb it might not be) then $20,000 in dev time to babysit open source might be cheaper than the $10,000 paid tool—because that tool is wasting more than $10,000 in productivity, it’s just harder to see.
The buyer often doesn't use the product so he has no sense of the value it provides, or the pain of using substandard tools. Unless it's his own company he might not care that much either.
