How big of a market do you feel developer tools are - IDEs, IDE plugins, build tools, monitoring tools etc? Is there space for small companies to build something and survive profitably here?
How about if we extend the market to include programming frameworks, libraries and database systems?
From a qualitative standpoint, think of this way ... all companies are now tech companies and developer jobs are always in any recent "hottest job" list you can find. So, it stands to reason that tools for those companies and jobs will be a big market.
If you want real numbers, here's 2 examples: (1) Atlassian is now a public company and pretty much only makes developer tools. They started with one product (Jira) in 2002. They now have a market cap of $11B and annual revenues of $620M [0]. (2) If you read Indie Hackers, you'll find people like Mike Perham who makes Sidekiq. Sidekiq is an open-source tool for background processing in Ruby on Rails apps. Mike makes $80K/month on premium licenses/support. Think about that, it does just one thing for just one developer framework and he makes close to $1M per year with no employees.[1]
So, yes, I think there's a big market (in the billions) and plenty of room for small companies. Off the top of my head I can probably think of a dozen developer tool ideas that I'd consider paying for.
[0] https://finance.yahoo.com/quote/TEAM
[1] https://www.indiehackers.com/businesses/sidekiq