Its obvious that Google can offer high salaries. Same with Etsy, while its nowhere near Googles level, I feel like Gitlab's cashflow is nowhere near Etsy's cashflow either.
I checked for London and I can say that Gitlab seems to be giving out a low to average salary at best. Which is not bad considering that you can be working remotely from your home etc etc, and get maybe more shares in a startup like Gitlab.
But ye all and all I feel the OP is a bit right that since they got a better funding they should be looking at accumulating their salaries to go up for their devs that have been getting bellow market rates.