This is how many developers think contracts work. Notably, most businesses do *not* think that this is how contracts work. This is why contracts are drafted carefully by professionals and are really effing expensive. 
I would ordinarily cite a comment on HN but I have a strict no shaming policy; take it as "a conveniently copy/pastable example of a very common flawed belief in the developer community."
Free professional output is available from many people, including yours truly, and it does exactly what it says on the tin, not what you might wished it did. That second thing? That's called a "deliverable." You can ask for it to be specified in a Statement of Work.
You can feel free to ask any professional for a rough estimate on what number they will write on a Statement of Work; many will happily indicatively quote you. If I were not full-time employed, my last number would have been $30k per week.
You don't have to like that number. You don't have to agree with that number. You just have to convince the people who control the money at your company to promise to pay that number before you have any moral claim to assign work to me.
