Does the cost of pet slots double every time you purchase one from the MC? & Is there any way to see how many pet slots you have left to purchase with CSC out of the 15 limit?

here breaks down your pet slots for you.

I believe the cost doubles each time, but I'm not sure really

The cost of the MC pet slots increases by 20 million sP for each pet slot, until you have purchased all five. (So 1st one is 20 million, 2nd is 40 million, 3rd is 60 million, 4th is 80 million, and 5th is 100 million.)

ah that makes sense too :p first one doubles.

Thank you both!