Cloudflare spends ~$400M/year on R&D while Chrome may be spending almost that much alone. Whoever buys Chrome needs to earn >$1B in revenue from it either directly or through some sort of synergy.
What's braves spend?
People underestimate how expensive it is to build a browser. There's a reason why we have only 3 major engines. Firefox (struggling), Chromium (Google backed) and Safari (Apple backed)
I don't know if it needs $400m but I wouldn't be surprised if it's $20m+ just to keep the browser secure.
Google paid out $12m last year in bug bounties and I assume they spend that much or more for in-house security researchers/developers (headcount is expensive) and periodic independent audits of the codebase.