Can you provide a citation for "$10,000 fine"?
Going 5 over the speed limit is illegal. However, you don't go to prison for 15 years on your first offense.
Just because something is illegal, doesn't mean it's a severe felony.
The FCC's actions towards individuals who improperly use radios are all public and there is not a single example of a person being fined for using a ham radio to transmit on GMRS in a manner that would otherwise be legal. Sure; just like the cop who dings you for the lanyard over the rear view mirror 'obstructing your vision' when they stop you for speeding; there are examples of people who were also doing other illegal things being dinged, yes. And the FCC is definitely going after / cracking down on vendors and manufacturers who sell radios capable of both. But no; it is not a priority for the FCC to aggressively prosecute people who use the GMRS service with a ham radio or vice versa, who are otherwise licensed to do so, and who are doing so in a manner that is otherwise legal (non-disruptive, not causing interference, transmitting at appropriate frequencies and powers, etc.)
I use two radios myself; mostly just because I want the performance of a proper GMRS antenna and the easiest way for my smooth brain to figure out how to do that was two antennas and two radios in my truck. There's probably a way to get my ham radio to transmit over GMRS; I dunno. Haven't figured it out if there is. And generally speaking, I prefer to follow the rules and I'm pretty by the book. But there is this bizarre internet disconnect happening where folks thing that something that violates a regulatory bodies statute is the same thing as a felony; or would ever warrant a $10,000 fine. People get fined by the FCC when they intentionally cause problems, or when they use their equipment to deny other people the right to use their equipment (such as jammers, something the FCC really does go after hardcore).