It's not difficult to make such an arrangement less expensive, the problem comes from turning a profit from your efforts. If you make something that costs you $150.00 in parts, requires 5 hours of labor @ $25.00/hour to assemble, $3.00 for labels, $2.00 for printing instructions, 3 hours of copy writing at various websites to advertise, $30.00 to ship, add for sales and business taxes, etc., you have to sell it for more than the ~$541.00 you have into it. Typical "add on" starts at ~5x production costs so you're at ~$2705.00. Of course you can discount that but if you only sell one or two of them you didn't make much for the month or more of effort you put into the design work, which is certainly compensable time, unless you like working for free. Within 3 months of your product release one or more Chinese companies will have obtained one, reverse engineered it, and started making their own cut rate version and put you out of business selling their at 1/10th the price of yours at Amazon or mtyourwallettech.com. Of course most of those will break within a month or so and with a no return of electrical stuff policy, or perpetual delays in CS response you'll be out of luck, but consumers only see the list price comparisons when they make buying decisions. So you add even more to your selling price to allow for the fact you'll be out of business within a couple months of the product release.
The real issue is a remote power system for a multirotor is it's a solution looking for a problem that for the most part doesn't exist. There are very few (and there are some) real life instances where a camera mounted on a rigid or telescoping pole or an aerostat fails to be less expensive in both direct and maintenance costs and have longer duration. Such arrangements are/can be easily automated for operation or controlled remotely from a single joystick by a relatively untrained operator. Exacerbating the cost differences, you can use a much, much better imagery system on both the pole and aerostat than you can on a multirotor and operate them from much further away while distributing the product in real time to multiple recipients across the world. Such is and has been done for decades, and it works. The application has to be practical for the condition, which means a comparative cost analysis must be performed when considering this kind of stuff.