I do aerial filming too and have been using BMPCC a lot lately. I disagree you can build machine for bmpcc as low as $500, even if most cheapest crappy parts were used. You can probably lift it to air for couple of minutes in calm weather but filming with it is not going to happen.
To carry BMPCC with a decent lens safely and reasonable flight times you need around 6-8kg AUW capable hexa or octo. I also prefer 3:1/2:1 thrust ratio for strong gusty weather and also brushless gimbal needs to be oversized if tend to shoot any other conditions than calm. When you have a shooting it's rarely ideal conditions, couple of days ago i had a shooting and forecast showed 17-18m/s gusts, fortunately it wasn't that bad, only around 10m/s.. But you can forget $200 so called "SLR" rubbish gimbals, it's not going to do the job.
My smaller machine 800mm hexa is flying around 13-14min with one flight pack carrying BMPCC, and my Octos are flying 15min with 2 batteries with bmpcc and 8min with Scarlet and canon 17-40mm/4. I would say minimum price for parts of bare copter and gimbal is around $4000-5000 if you build all by yourself. Plus you need batteries, chargers, radios, tools, second and third spare copter, second gimbal, garage, van....
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