I hope this is the right board for the question.
I have this idea for a game, programming Skills with C++ and a licensed Engine. I already made a prototype of the game as proof of concept and a few friends liked it so far.
I don't want to spoil it all, but it is a 2D Robotron Style Precision Shooter in an arena which is set in space.
All you do is beating waves of enemies and when you leveled up, you select a perk to enhance your ship. Examples are making weapons stronger, faster, making the ship more agile, different Weapons as Smartbombs, Mines etc.
Having different maps with this kind of game is quite difficult, since space does not have obstacles. All you can do is make different backgrounds and maybe asteroids etc. Another type of content could be to allow the user to gather some virtual money to unlock goodies that are available at wave 1.
So far for my idea. Now, would this alone already justify asking 5$ for a game? When I compare it for example to puppygames game "Titan Attacks", I say yes, since they do not have more features. On their website the game is 7$, on Steam 4$. Their Ultratron is also 7$, which is also a classic robotron style game. But it does not yield any special features imho ( it is fun nontheless :D ), but has a very adorable artstyle.
Nation Red, which is also an inspiring source for me (Robtron Style 3D Zombie Shooter, awesome game btw), costs 10$ on Steam but also has coop, local and online.
So, how do you estimate the price of your game that you just made so people don't feel ripped off and you still make profit after getting back the investment of licenses?