I think I found a solution and I hope this works for you.

If you have the configuration item with a recurring price as default, for example $100 per month, add a multiple choice variable with the choices of lease or purchase.

For option 1, enter recurring as the option. No price change will occur.

For option 2, add purchase as the option. Add the full purchase price in the "Price" field. Add a negative amount in the "Recurring price" field (in this example -100)

When a customer selects the purchase option, the recurring fee goes to $0 but when the item is added, the full purchase price appears instead. You won't see the full purchase price until you add it to the cart or the item is ordered.

You can do the reverse if you plan to add the full price in the configuration item first (e.g. negate the full price and add the recurring price) and make the recurring pricing as the option.