think of it like this...
Transfer Budget is a current account (meaning money is easily accessible hence not much interest can be generated on it as it could be spent at any second)
Wage budgetis a set account (the money is always in there, the wages would be debited off that seperate account every week, if there is no money in there, it would have to come from somewhere else, so if there was an excess, the money would and does generate interest as there is ALWAY's money in the account
get what I mean?