Of course, you haven't infringed on anyone's freedom yet, there are no users. I guess the thing is if you massively overcharge without providing any corresponding service of value the first person that purchases it has the option to throw the source code up on the internet and it can be forked.
I guess you also have to find a buyer that is willing to pay you the large sum while also knowing they can't charge others for it without also handing over the source code, so it's doubtful anyone would do so.
There are other options though, if a single person or entity owns the copyright for the entire code base, with no outside contributors, they can dual license it. GPL for the public and then commercial proprietary license for businesses. That way the business can build on it if they wish without redistributing the source.