My team and I are currently working on a commercial project with a Kickstarter planned next month.
What I have done is mostly commissioning.
This way, you pay for one image/music track or whatever it is you need.
When it comes to pricing, it varies a lot, and by that, I mean a LOT!
Depending on the quality you are seeking(and the people you commission), a full-body character image could cost you anywhere from $20-$100.
Music is often paid for based on the length of each track, and the price varies just as much as it does with 2D art.
Mapping, eventing, databasing and scripting are time consuming, and you'd likely look at the same price range as the other things there
So... based on this, it will be very expensive to hire a team to do everything else than writing the story!
If each map costs you $25, and you need 100 maps, that adds up to $2500
A full soundtrack will be expensive. Let's say $150 per track, and you need 15. That adds up to
$2250
Then you need some character art! Battlers who can also be used as busts or facesets for example. Let's say that each costs you $35, and you need 15. That adds up to
$525
Let's then assume that you need some custom scripts. Let's say you need four, and each costs you $30(I haven't done this, so this price is but a guess). That adds up to
$120
Based on this, the cost to produce the game would be about
$5395 - and this is pretty optimistic