"If you are the kind of person who can do it, you don't need to read posts like these."
If you are the kind of person who can do it you don't even need to be a developer either. Entrepreneurs can hire developers. Even if you need some cash for that, it's not hard to find it.
I don't think you are missing anything. There are advertisers who prefer other networks like Chitika, Adbrite, Clicksor etc because of the lower competition/lower click prices there (and not only).
I use captchas that set a hidden field value through javascript (the user does not enter anything). It takes a second to view source and figure out what should you enter. Despites this, the captcha works 100% and spam stops. Unless spammers target your own site manually, such a solution is good enough.
One more model: SAAS. You can have open source product that is free to download and use but offer hosted version, paid, for those who prefer someone else to have the hassle of installation and configuration.
Of course you don't need to be the creator of the open source software to do this.