I realise that I didn't share this with the original Temple Run 2 score calculation post, so I thought that I would share it here.
Save Me is an element of the game where you have the option to resurrect your character if you "die" during your run. It uses an in game currency called gems, and it's how Imangi makes money. They put money into developing the app, people buy the app (which is free), and they can buy extra in game currency to extend a really high score, or so on.
Now, at the start, revival costs a small number of gems. As time progresses, though, the cost to revive yourself can get quite high. This resets each game - so it won't cost you a ridiculously large amount of gems to preserve your score every time you revive.
The formula is very simple, so I'm just going to give you a little explanation of how it works.
Now, to calculate the amount of gems needed for an individual "revival", you'll need to use the following formula:
By practicing with reviving for a little while, I've determined that the formula grows exponentially - every time you die, the base score for you to revive doubles. Now, that's affected by the level that your "Save Me" powerup is - that reduces the cost to revive. So, while it doesn't increase exactly exponentially, it is stunted somewhat. That's because once you've revived four or five times, it becomes significantly more expensive to revive, and increasingly unlikely to do so without the purchase of gems.
I've written up a short comparison table that compares the cost to revive, based on what revive attempt you're on in a single run.
The table above is based on if you have not levelled up the "Save Me" powerup. As you can see, the cost for a single revive (in column 2) is quite small. As you progress, the cost increases quite rapidly, until you're spending a large amount of gems in a single go.
I'll back be soon, with a fresh new post!
All the best,