I recently made a homemade macro studio that cost me about $20. Just wanna share in case someone might find it useful too.

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1. BBQ Grill (500mm x 300mm) from Denso ($2 each, I got 6 pcs)
2. Plastic Corrugated Boards from Popular (Don't really know what its called) I got a white for reflected light, and a transparent for diffusion ($1.60 each)
3. Mahjong Paper 36" x 36" from Popular ($2.50 for 5 pcs, not very white but cheap enough)
4. Binder clip from Popular ($0.85)
5. Twisties (I just found it lying around, had it for 5 years now so can't remember how much it was)
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6. Use twisties to bind the BBQ grills. Bind loosely enough so it can swing freely.
7. Use binder to stick the paper on the grill, and some more binder to weigh down the paper. And then use the corrugated boards on the "walls".
8. When not in use, you can detach everything and stack the BBQ grills.
Sample photos.. kinda dirty but for a $20 studio, it should be good enough. My light is either on the right-front side (left photo of orange) or right-back side (right photo of orange)
FYI: I used SB800 flash set as wireless, 85mm, tripod and +1 closeup filter. But when I was starting, I was using a cheap lamp with decent wattage philips bulb and a tripod.

My flash and "dew" maker.
Lastly, all things above are items I managed to find that keeps cost down, while making it flexible (corrugated board has many colors; grills can be reused for the next bbq or portable small cage for my rabbit; bigger studio means adding more grill elements, etc etc). Anyway, have fun guys.