Hello there 
I’m just a little curious.
If I wanted somebody to develop a specific part of my game,
how much money will it cost?
Sure, it depends on hours, but what if I don’t know how many hours it will take for that?
- Linus
There is no real way to adequately answer the question as initially posed. The charges people would have would vary based on (as you mentioned) the hours of work, the number / complexity of features implemented, and the reputation/skillset of the contracted worker (people who have a reputation for producing good quality work will likely charge more than someone who lacks that work history to support them).
In addition to that, different elements of your game may require different levels of payment. Programming jobs are generally hired at larger costs than contracts for artwork, music, writing, or animation. The nature, scope, and level of detail in your requested contract will all affect the end cost radically differently.