Leave and go where else in software testing in Japan? Based on the article they are paying a lot more than other software testing companies. Also, if they are paying people well and treating them well, a sizable chunk would like to continue even if the salary increases dwindle as long as they are not underpaid compared to the market. I also think that Japanese culture would inspire more loyalty to well paying, well treating companies compared to SV.

Japan has had much lower inflation rates than India over the past few decades. Famously Japan has had close to 0 inflation.

It seems like the real reason for this firm's success though, is removing multiple layers of contractors. Just hiring skilled engineers and paying them fair rates seems sufficient to shake up the industry. That seems sustainable to me - provided they keep salaries competitive - presuming some of their competitors try a similar approach.

He could scale beyond just software testing, maybe make a product or two leveraging his investment in a better-than-normal engineering base by copying more best practices from silicon valley while leveraging the language barrier that prevents these engineers from moving onto FANG in the first place.

Surely it's a good thing to have employees leave who think $X is less than (X/2)*1.15

I think the point would be you are already earning above average for the industry. No guarantee the next job will match that salary for the same type of work. Sure you can go the promotion route but the. You don't need to leave the company to pursue that.