How do you even get a job as a bug finder and how much dose the earn?^^
i guess that is allot cheaper than making a beta.
Where I work (I'm a software developer), we hire college students as part time interns and pay $12/hr (USD) and less.
The thing about a public beta is, you still have to pay someone to sort through all of the bug reports that the public submits.
And you're still going to have to have QA in-house to work on replicating the bugs the public found and really getting to the bottom of them.
The amount of money you spend on people to collect, sort, and file public-submitted bug reports is typically better spent just having an in-hosue QA person do the testing themselves and working directly with the developers.
As I said, the only time you absolutely must have a public beta is when you're releasing some sort of online game and you need to stress test your servers. This is the sort of test that you really can't realistically do purely in-house. You can simulate it, but until you
actually do it, you just can't know for sure what the server stress will be like.