I spent 5 years writing insurance coverage for US companies whose employees travel overseas.
There's almost no reason that you would need a med-evac out of Paris. They only do med-evac when the care you need is available in your home country but not the country you're currently in. Frankly, the quality of care you're likely to get in Paris probably exceeds that at home.
Worst-case scenario is that you are severely injured in Paris. You would be treated in local hospitals (European ones don't typically require up-front payment the way some developing countries do, but if somehow they did, they'd take credit cards), and then your health insurance will reimburse you (usually out-of-network). You'd miss your original flight home and need to rebook something else. If your injuries were such that you couldn't fit into a regular seat but could fit into a coach bulkhead seat (like if you broke your leg), you'd be able to get that bulkhead seat for free. If your injuries were such that you required a lay-flat first class seat, you may have to pay for that seat, or you may be able to talk the airline into giving it to you as a medical accomodation.
I've never bought travel insurance for any travel I've ever taken, and my husband has a lot of health issues. My analysis of the risk is, there's a less than 1% chance of an issue costing me $10,000, so I shouldn't pay more than $100 for coverage. Since I've never found anything even close to that, I've opted to self-insure.