If you have a node with 30mb of TXs ( all of them different Size, paying different fees and whatnot) and you get a new block that is 28mb in size, Graphene help your node by not having
to re-download those 28mb because you already have that information in your mempool. With graphene you just send some information about what TXs are included in those 28mb. So you only
receive a packet of 0.5mb with Graphene. Do you see what I mean? In the end the blocksize ( written to HDD) will be 28mb, the TXs will have paid whatever fees they wanted, but this is
not what Graphene is about. Graphene help nodes communicate blocks faster because most of them have the same mempool of TXs. So you don't have to re-download all the TXs in the block.