how often?

[qwerty]

hi im qwerty and i i am interested in buying a tamagotchi yasashii, i know they are very expencive! but i have the cash! and i would just like to know how often the appear on ebay like 1 every month/ 2 months/ 3 months etc

thanks

p.s. can all answers be PMed to me?

thanks again

qwerty