Blimey, your toothfairy must be flush! Ours pays up a quid, but only if the tooth in question is carefully placed in an envelope with a polite note on it. Manners cost nothing, doncha know
On one occasion the eldest cub did get more - but that was when we were away on holibobs staying with some (child-free) friends in Hertfordshire. Apparently their tooth fairy was so excited by the unaccustomed business that he paid up a fiver, and left a note to say thank you. But that was different, because it was a wealthy southern tooth fairy, not a skinflint Yorkshire one.
(multiply the number of baby teeth by 5 and by the number of babies - does your tooth fairy really want to create that expectation?)