Why would someone charging $75 say I'm riping them off at $50?
You can charge what you want hourly, thats fine, but to raise the price of the product itself isn't right.
By charging $200-$300 to apply Opti-Coat, you aren't charging more for the PRODUCT. You are charging for the APPLICATION of the product. Opti Coat is a permanent coating that must be polished off completely if a mistake is made. That costs more labor, and significantly more product. Opti-Coat requires a certain degree of SKILL, specialized skill, in order to apply properly. That is why YOU as a detailer, are applying it for them, because if they try to apply it themselves, they will likely mess it up, and then maybe need to have the whole car polished and then try again until they get it right, or have someone else do it.
Charging more to apply a tricky product is about charging more for your skilled labor, which is a cost in addition to the cost of the product used. What if you make a mistake and need to redo a panel? Will you charge the customer extra labor to fix your own mistake? I hope not, but that is a cost of doing business, and so the risk of that needs to be factored in and included in the higher price for the application of the tricky product. If you want to, you could just sell a syringe of Opti Coat to the customer at your cost, if you disagree with charging more. But ahh, the customer wants YOU to apply it instead! How much do you think you should really charge for your effort in doing so?
The coating and the car are the raw materials, and the coated car is the finished product. (plus, it's a permanent coating, so it pretty much IS a different car now.) Companies who make products always charge a lot more than the cost of materials to make them.
As an aside, I was totally shocked when I read that you charged $50 an hour to detail. The highest I heard before that was $35. Maybe you think that at $50 an hour, to charge significantly more for this coating is gouging the customer? Maybe. It's your call. Different artists make different amounts of money for their work.