Fair enough. They publish their annual financial report but it isn't splitted per project so it's hard to know for a fact with the public information we have access to. However, it isn't unreasonable to think that at the very least a percentage of the smaller products revenues are reinjected elsewhere in the organization (e.g Firefox) since the goal seems to be to diversify their income sources.
> People keep saying this, but given that it's never been tried you have no proof. And even if it were, what harm is there in opening up one more option for those of us who want to be really clear about what we're paying for?
It's been tried over and over in the FOSS community. Few projects are able to get decent money with donations (e.g. Thunderbird). However, it's nowhere near the complexity of a web browser.
For example, Thunderbird made almost $7M (USD) in 2023 for an average of $20 per donation which is 350k users out of 20M monthly active users [1]. Firefox has 10 times that number of users so we could estimate that they'd make $70M/year. That's far from $500M/year they're doing right now.
[1]: https://blog.thunderbird.net/2023/05/thunderbird-is-thriving...