https://jlcpcb.com/partdetail/Worldsemi-WS2812BMini/C527089 https://jlcpcb.com/partdetail/Worldsemi-WS2812BMini/C527089 $0.01 per LED About $2 per 100x100 mm

https://jlcpcb.com/partdetail/Worldsemi-WS2812BMini/C527089 https://jlcpcb.com/partdetail/Worldsemi-WS2812BMini/C527089 $0.01 per LED About $2 per 100x100 mm board if you order about 100 of them. About $1 per above board for assembly service. Total: $6 per 15x15 LED board of 100x100 mm. Total: $12 per 30x30 LED board of 100x100 mm. I have no idea about how many would you actually need. As for the power supply, each LED draws 12 mA. So you are going to need quite a beefy supply. 15x15 grid = 2.7 A @ 5 V 30x30 grid = 10.8 A @ 5 V