The amount that you have to pay for the cartoon depends on the use to which it's going to be put. You'll find a list of uses below.
If your exact use isn't listed please choose the one that you think is closest – it's impossible to cover all possible uses in a list without the list becoming endless! If in doubt, or if your use is unusual or complicated, please contact me.
Purchasing the rights to use the cartoon doesn't entitle you to use it indiscriminately forever – copyright rules state that you're purchasing the right to use it only for the agreed purpose. If you want to use the image for any use beyond the agreed purpose you have to pay separately for each use. There's more on copyright here.