It's definitely true that what Sentry is today, is a function of operating it at scale. Thankfully one of the intended purposes of Sentry is also that it scales down much better than today [1]. That it does not is also something that Sentry as a company is not happy with which is why there are desires to change that, which will also benefit self hosted.

[1]: this is because a) developing on sentry has become harder and harder on local machines and b) operating single-tenant installations for some customers brings many of the same challenges that people on self-hosted run into. c) we want more regions of Sentry and smaller ones (such as Europe today) have higher fixed costs than ideal.