You should verify you're dealing with the rightsholder or their representative, then take their offer, IMO. Paying a reasonable fee to license the cartoon, whic

You should verify you're dealing with the rightsholder or their representative, then take their offer, IMO. Paying a reasonable fee to license the cartoon, which is what they've offered you, is both legally and ethically the right thing to do. You can't copy and distribute someone else's work without their permission. There is no requirement of malice, financial gain, or anything else to be in violation of their rights under copyright law. It's just not allowed, and that's the case in probably 100+ countries around the world, since 90-something were signatories to the WIPO treaties. Your use of the image doesn't fall under any of the fair use exemptions, and neither is ignorance of the law a defense. If they wanted to take you to court, you'd lose, and you'd almost definitely owe more than $168.