Pivot the conversation to a purely financial decision, where an investment of a few hundred or a few thousand dollars can generate awesome returns through dual pricing.

There are three ways I see these type of deals getting done.

The merchant pays early termination and other costs incurred breaking the contract, and recoups multiples of that amount by eliminating most of their interchange costs.

The merchant and agent share the quantifiable costs of breaking a contract and any needed upgrades to the merchant's POS solution, as well as returns on the investment.

Ask your ISO/processor to cover the cost of breaking the merchant's existing contract and any required hardware and software upgrades. Or work out a deal where you pay back some or all of those costs to the ISO from future residuals.

If your ISO or processor doesn't want to work with you on these type deals, it may be time to start looking for a new partner.