I don't have an answer just for op costs per airframe. As only a pilot and a drone, It's really hard not to sell yourself short, IMO.
Without proper enforcement, we'll likely never get paid enough to cover our equipment costs by just flying around and giving away the raw footage.
So, like all of us here, you'll need to carve out niches that add value for the Customer. Flying an UAV is not enough. We must deliver a complete package to get a proper return.
I get a much better return on time spent doing related tasks like training, IT consulting, video production, and securely delivering their information. This pays for the hardware. Otherwise, I couldn't be in business.
Here's a link to an actual study from the field back in 2016. It seems to be a helicopter-friendly study, but good for some reference.
Much has changed, but this shows the type of information you may come up against when selling your services.
At least some numbers to play around with since it shows what they were willing to pay for UAV services back then. Also, some good helicopter operating cost info to compare.
BTW, in this report, they say that helis are cheaper than UAV's for this specific task! It may still be true, but you can practice overcoming studies like this one.
http://wildfire.fpinnovations.ca/AdvisoryMeeting/2016Spring/Jim-UAVCostComparison.pdf