The "cheapness" of a coin isn't given just by its price. You must calculate (price X noOfCoinsThatExists).

If everything else equal (in particular the total amount of money ($) "in" the system):

Coin A has price $1, and 100 coins exist.
Coin B has price $10, and 10 coins exist.

Total value = $100, for both.

Unless you have more information there is no reason to think there is a greater probability coin A will increase 10x than coin B will increase 10x. The amount of new money required into the coin would be the same in both cases.

So the probability A will go to from $1 to $10 is the same as the probability B will go to $10 to $100. in both cases an additional $900 in new money is needed.