The 100% copper models notwithstanding, the combination of brass with whatever low thermal conductivity metal is not the best mix for excellent thermal conductivity, but it is very durable and relatively resistant to environmental damage of one kind or another + the focus is to keep costs down yet give good value for hard earned money spent.
JetLasers and Sanwu accomplish that goal more completely than most commercial makers.
Everything is a tradeoff in most commercial/consumer/end user product but Sanwu has done their homework and produces excellent product values for the retail end user cost when compared to the sea of mediocre and worse generally out there and for sale + way better than vast number of absolutely garbage quality lasers sold at high prices being marketed in today's world to people who don't know any better.
Attn: LPF Members>>>The above having been said if you want a simple to assemble/complete high/excellent quality laser in a superior host please have a look at LPF member Lifetime 17's offerings.
All of them are better quality than the vast majority of commercially manufactured lasers when completed with high quality parts easy to come/find by these days.
See:
https://laserpointerforums.com/media/albums/signature-pictures.9/