I'm developing a website with PHP, but it could be a lot of work for me i should handle invoice and financial part of transaction.

I live in italy and i should invoice for each transaction even for small amount like 1

I'm thinking about a service that act like a reseller
Kind of what happens with Apple app store. Apple sell, invoice, and handle all the financial and legal part between them and final client. Every X days developer get payed by Apple.

In this case a just have to invoice to that service.

I really have to think about my business model for premium service but i would like to have small fee, some of them could be in range of 1,5 - 2,5

I found fastspring and they seem to do what i'm looking for but have a high transaction cost even for small amount.

I also found 2checkout but i'm not completely sure that handle financial and legal part for seller as fostspring does

any suggestions?