@pigsick57
First off, 10 days of 5X for 25 donuts is the best bargain.
Secondly, what level are you on, that affects the requirements. From levels 61 to 100 bonuts are 40,000 each; between 101 and 939 bonuts are 500,000 each, then it's 1,000,000 after that.
How much XP are you making per day without the Collider going? Write down what you have at the end of the day, then again at the end of the next day. Then use this formula:
XP Base x (1 + M% x 5) = XP Collider
But if you only recoup what you spent, what's the point? You need to make significantly more than you put in to make it worth doing.
And what if you're in a minor accident and sprain your hand / get burned / whatever and can't play. Think about that. You need to be able to recoup at least what you spent quickly (like in the first day) so you don't waste those donuts you spent.
I'm not trying to talk you out of using the Collider, just trying to set you straight on your needs.
Personally I'm making about 115 donuts a day with mine on (1333.36% with 35 KEMs every 4 hours), so spending 25 every 10 days to activate it is well worth it - even if I have yet another boo-boo and can't play for a while.