When we sow financial seeds into a ministry, we partner with a message that we didn't develop. Our financial seeds allow us to walk with leaders who may walk in more spiritual authority than we do - or at the very least, they have a circle of influence that we do not. And when we sow financial seeds we open up the possibilities for revelation and breakthrough to be brought to us in areas that we haven't been able to reach before.
Sowing financial seeds is not linear - it's exponential - it's kingdom. God doesn't operate in a one dimensional line. And He doesn't even operate in 3 dimensions. There are infinte amount of ways that God blesses, brings provision, provides wisdom and revelation when we sow financial seeds into kingdom messages that break the hell off of people.
If you doubt it, then see if you can account for every single revelation that you've received from pulpit, from a CD, or from some Godly wisdom you've received. It's all come from a seed - and most of them couldn't have got to you without someone sowing seeds of finances.