Read what you put, just seems a bit of a nightmare, timers, different currencies, the game getting harder so you have to buy/wait more etc. Sounds a freemium nightmare
The game is free to try till a level cap of 10. The full story quest costs $2.99. I got the $4.99 IAP that unlocks all bonus features like a different mode and an arena. It's quite similar to Jet Car Stunts 2's IAPs.
Outside of leaderboards and cloud saving, you don't need internet to play Reaper. Another brilliant thing about the IAP there is you can upgrade to a higher version for just the difference in price. Try the game out first because some people just don't like the controls.