Cost in the article is cited at 550 euro. I just browsed amazon.de and you can buy complete plug and play kits here in Germany for as little as 239 euro. Most kits are priced between 300-350 euro. I did not see a many kits over 500.
I pay about 70 euro per month for electricity. If it saves 10% per month on my bill (7 euro), this would earn itself back within 3 years. At 5% it's 6 years. Not bad for something that costs next to nothing and is pretty much plug and play. You are not going to get very rich from this obviously. But it's kind of cool. Too bad my balcony faces east and is mostly covered by the shadow of other buildings. I can barely grow plants there.
They could try. I just keep hearing people who would pay for no extra features as long as it paid for actual Firefox development and not the random unrelated Mozilla projects. I would pay a subscription. But they don't let me.
There are people like yourself who would be happy to donate, but not nearly enough. Replacing MoCo's current revenue with donors would require donations at the level of Doctors without Borders, American Cancer Society, or the Make-a-Wish Foundation.
Turning into one of the largest charities in America overnight simply isn't realistic. A drastic downsizing to subsist on donor revenue also isn't wise when Mozilla already has to compete with a smaller team. And "Ladybird does it" isn't a real argument until and unless it graduates from cool project to usable and competitive browser.