No. I'm not free to pay nothing. I'm free to pay:
* My IT guy $200 per hour. If maintaining a technology takes a day a month -- which is wildly optimistic -- that's $1600 per month
* The organization which developed the tool e.g. $50-$200 per month
* A random outsourcing organization $10-$50 per month
By making your software free software, I will still pay you, but I know that:
1. If you do decide to spike prices, I can go to the off-brand company or to my IT guy. You better provide better service than the off-brand at lower prices than my IT guy.
2. If you do go out of business, I can go to my IT guy.
It's all about power dynamics. You don't have the option to f- me, and by having taken away that option, you've made it more likely I'll buy from you. It's often just simple good business.
Oracle's business model is largely about buying up companies with large locked-in entrenched bases, spiking prices while lowering costs, and milking cash cows as the cows gradually die. They did that to Java and a few others. Free software means I can't get Oracled too badly.
Some companies take a middle ground by e.g using open APIs. For example, AWS has services which have better price/performance than free software, but maintain compatibility. I'll be more likely to use those than proprietary alternatives because if AWS decided to Oracle me, I can switch to the free software version. There are systems like git, where essential business value is free software, so I can move my code out and around if Microsoft decides to oracle me, but where there is a significant proprietary value-add.
Your value to customer goes up with:
100% free > hybrid models > proprietary
Your barriers to competitors go the other way.
This isn't just signaling. It's power dynamics. Companies send out false signals all the time. This is a hard barrier.
The right business model depends on your market and technology. I've mostly done free software, and that's mostly a matter of choice -- I've picked businesses where 100% free makes business sense.