As a general rule, purchases are non-transferable between accounts. This is because certain offers may be made available when an account meets certain criteria - such as the starter pack, which is available only to new players - and so cannot be moved to other accounts.
That said, if you have accidentally bought something on the wrong account, our Support team may be able to provide assistance. Please keep in mind that they will not transfer one-time offers (such as the starter pack) but will be able to assist in other cases.