A conservation easement is not a payment. Sweeney didn't actually pay $15 million. He just gave up the right to develop on a piece of land he wasn't ever going to develop on anyway. This gives him a $15 million tax deduction over several years that he can use to offset his tax liabilities. Since he donated $15 million worth of property rights, he probably has a lot of them.

Not very different from Trump's conservation easement donation in New York.