The federal government is that contract between states

The federal government is a contract between 50 states. You are envisioning a shared project in which the people in a majority of those states reject the project. You are envisioning a project wherein the people of a minority of those states wish to enact this project against the will of the people of a majority of states.

Your argument is that this minority of states will be funding this project anyway, so the majority of states have no interest in stopping the project.

What I am saying is that you don't need the 50-state contract to proceed with this project. The 10 states that think it is a good idea can establish a joint commission to enact the project without ever consulting or otherwise involving the remaining 40 states.

The federal government is a contract, not the contract. Establish a different contract between the specific states that support your project, and stop trying to impose your little project on people who don't want it.

those smaller states are generally net receivers, not payers, so when they veto projects not dependent on them for anything and which don't cost them anything, your entire argument is dead in the water.

Rejected.

Consider a classic, 1950's family. Husband, wife, 2.5 kids. He is the sole breadwinner; she is a stay-at-home wife and mother. She is a "net receiver" of the family's money; he is the "net payer". He is the sole economic contributor to their joint checking account.

If we apply your argument, she has no valid interest in determining how that money should be budgeted. He should be fully empowered to reject her opinions on how the money should be spent. The decision to squander their joint finances at the bar or dog track is his, and his alone.

Obviously, this is abusive. She contributes considerably to the family, yet her contributions are devalued and her needs ignored. She is deemed some sort of nagging buzzkill rather than an actual partner.

The abusiveness of this relationship doesn't change when we shift from this small family to a 50-state polycule. What does change is that the "breadwinner" states are free to establish a separate, joint commission with each other, separate and apart from their federal obligations. A handful of "breadwinner" states are actually free to engage in their shared project, without involving or consulting the "housewife" states. So long as they don't touch the "joint checking account" that is the federal government, they are free to use their own money in any way they want.