Calm down man, there is nothing shady about how the mogstation works. Only perhaps inconvenient at times.
Your account is propably flagged as brittish, I have no idea if you can change it but knowing how rigid acount info is possibly not.
Indeed on the payment selection screen it doesnt say how much crysta is needed, but the next screen will and you can still cancel transaction there.
In euro its €1 is 100 crysta, so am guessing the value of crysta depends on your account location so that renaming you want would be 575 crysta

I prefer websites not to remember my credit card. And i dont care for paypal myself, why would i need a man in the middle when i can perfectly fine pay with a credit card myself.
Is paypal 100% free to use? Any costs would be charged to SE since.