Clicking "Cancel plan" on a product puts this plan into pause until the end of your current rental period. The plan can be resumed at any time without any new charges being added.
After the end of the pause period your Rack Extension goes into being cancelled. This can be resumed at a charge of US$/Euro 9.99 at any time re-starting your payment plan with all funds going against the total purchase value.
However, please be aware that purchasing a Rack Extension in the Reason Studios Shop while it is paused/cancelled as an Rent-to-Own product will cancel the Rent-to-Own plan without any funds being refunded.