Unpaid, hobby work can produce Dillo. It cannot produce Firefox or WebKit. A Dillo does not diminish the value of the paid programmers at Mozilla.
Open Source allows money making vendors to collaborate. For instance, the Apache project produces open source code from many profitable vendors. Each project may not be viable when executed by any single vendor. But together, it makes the work lighter and the individual vendors can focus and compete on their core strengths while sharing the common load. Note that everyone is making money in the process.
> even though about 99% make zero money
Where are you drawing these numbers from? Most of the quality open source code is from paid people working on the clock. Are there many small projects done off the clock? Sure. But a very large chunk of critical and widely adopted code is created and maintained by paid people, with occasional exceptions leading to bugs like Heartbleed.
There are projects that are meant to be open source projects (especially common infrastructure bits that we can all agree on) and there are projects that make economic sense only as proprietary projects and there is stuff in between. Open source is adding value, not diminishing it. You are seeing software value as a closed system when it isn't. Many of the traditional ideas of material markets don't exactly translate to software markets. Given the vibrancy and growth of software markets, it is that the other [markets and human enterprises] should take lessons from software markets when valid, not that the software markets should learn from classical markets.