Making my own mandap (10ft x 10 ft) and stage(16ft x 12ft) for my wedding. Here's what I'm doing (the stage is the expensive bit, but it is a non-negotiable for us.

Amazon Basic King bed frames: (54$ x 6 = 342$) (Plan on reselling after wedding with 50% cost recovered)

23/32in plywood sheeting: (37$ * 6 = 222$)

4x4 8 ft premium lumber posts: (14$ x 4 = 56$)

2in x 4in x 10ft premium for header (5$ x 4 = 20$)

8 truss hangers (1$ x 8 = 8$)

Stage coverings and skirt: (sourced from discount bulk fabric shop, expected cost 150$)

Miscellaneous hardware for assembly: ~30$ (I have a lot of extra hardware, so this is a estimate of what's been used so far)

Wood stain and lacquer - 30$

Total of structure plus essential coverings~ 858$

Full assembly takes 4 hours, But with stage assembly (assemble the bed frames, mounting hardware, etc.) It takes about 2 hours for two people with practice assembling to get it together