I imported an Australian kit plane into Sichuan made entirely from 6061 T6.It seems that the aerolite design doesn’t use any welding (not even the engine mount) - only 6061 aluminum tubes and CNC brackets. Both are extremely cheap to obtain in China.
I ordered a heap of extrusions locally here in Sichuan, 6061 T5, as well as 6061 T6 0.5mm sheet.
Sent samples of both for testing, the Australian was actually 6060, not 6061, and barely met minimum T6 temper, while the Chinese was "good quality" 6061, and above T5 temper for the extrusions.
And yes, cheap, very cheap.