I’ve made Wagyu burgers before and was not impressed. IMO, the best grilled burgers are made from a mixture of 50% ground sirloin and 50% of the cheap, 70% ground beef rolled into balls and smashed between two sheets of wax paper using a small cast iron pan.
Best burger I had was a Juicy Lucy in Minneapolis
My wife usually does a 50-50 mix of 80% fat ground beef and Jenny-O ground turkey. Cuts way down on the fat intake and is quite good.
” ...the best grilled burgers are made from...”
My favorite is ground rib trimmings. There is a local market that buys only rib primals, and all the trimming get ground up and sold for $3.99 (a few years ago it was $1.99). A large portion of the grind is what they trim off of ribeye fillets — the cap and the lip.