There is so much more in the market now. There are many flagship killers who are just as good as Samsung Huawei etc. You only buy an iPhone for that status and OS. Nothing more.
First of all , he ain't ESD-connected. Second of all, this ain't a professional repair. 3rd; You can cut yourself easily. especially if ur repairing iphones all day long. this goes against the safety policy of Apple. The only thing that he is right in , is that the replacement for broken back-glass is overprised. HOWEVER , if there is a in-warranty issue , and the back glass is broken ( and it's not involving the in warranty issue ) , the replacement will still be done inside the warranty.