How much money I can ask for an oculus app ?

The reason why I said "as much as you think" is because there's no way you determine the cost in fair fashion. It's downright impossible. Unlike hardware, where every single unit costs you something to produce it, non-physical items are only have some design costs, but potentially can make infinite amounts of money at no additional expense, thus their "fair" price lies right next to zero dollars. To note here as well, traditional market rules apply very loosely, if anywhat at all, to this area. So to determine how much you want people to pay for it you assess how much would you sell and how much of a scumbag you are, but mostly latter. This is because the general rule is to stick to tendencies. AAA-title may deserve $40-60 price. Indie game could cost between $5-20, depending on degree of scumbagery of the seller. It's not like you gonna get less sales because your game costs $20 and not $10 anyway, this is not what determines sales quantities (but outrageous prices may certainly limit sales count, yet you can still make more money that way). If you feel like extra scumbag, you may split the content into shitloads of paid DLCs, to ensure that you get most of the potential money from each individual customer.

And that's it. There's no formulas to assess the price accurately. And those classic economical formulas don't even apply here most of the time. Just choose how much money do you want to rip off of people.