Advice on photo drone build

I am doing the planning for a drone build and was hoping for some advice, this would be my first build, looking for advice on weight and cost savings, also flight control, Pixhawk 4 is quite expensive etc.​What I have so far.​PartWeightCost (AUD)S500 Frame408g$48ZOp 8000mah 3S 60C622g$70SunnySky X2820 920kv138gx4(552g)$184SimonK 30A ESC25gx4(100g)$48APC 13x6.5 props4x30g(120g)$25Neo M8n GPS + Compass26g$20FLY SKY 2.4G FS-CT6A T/R10g$60Total1.81kg$455Amps 480A(Battery MAXC) 184A(Motors MAXC) 120A(ESC) 104Amps(Motors at max thrust)Thrust 6670g 3.7twrNot sure how to calculate flight timepixhawk? FC4K action cam?Camera Mount?FPV?​​​ via /r/drones https://ift.tt/2ojeUUt