That's quite a bit different - there's probably a contractual (legal) obligation there.
I use my bandwidth to retrieve the web page, and my CPU/GPU time to render it. Arguably, my computer is doing some of the work for the "content creator" in any case. If we're going the Car Analogy Route, then I think the situation is more like you've bought some blueprints and chunks of metal. You machined the chunks of metal into parts, and then assembled a car. Does Ford or VW or GM get to demand that you put their badges/plates/etc on it?
This is to point out that physical analogies are slippery at best.
The assembly / bandwidth / cpu / etc argument really shines for limited platforms. E.g. if you're on metered internet, loading ads costs you money. If you're on a small device, playing ads costs you power, meaning you have to find a charger sooner.
Computer ads aren't free for the people subjected to them, since we're the ones that have to do the work of displaying them. Compare that to paper / magazine ads add a few grams of weight and a bit of volume, but rarely in noticeable amounts, and billboard ads that don't cost the recipient any resources by being there (except maybe having to step around them).
> paper / magazine ads add a few grams of weight and a bit of volume, but rarely in noticeable amounts
Have you even seen dead-tree magazines in the lase ~decade? They are often half (or more!) ads. I hardly call >50% of the volume/mass to be "rarely noticeable".
I'm sure there are counterexamples of saner magazines, but they are certainly not the common experience.
How many car manufacturers do you know that give away cars for free - which are build pre-packaged with advertising - without fist getting you to sign a contract that stipulates the terms of that arrangement? Only with that contract can they prevent you from modifying the product they gave you.
That is the entire point of the "first-sale doctrine"[1]. You can only control your product up until the point you hand it over to the first customer, and what they do with it after that point - provided[2] they stay within the law - is up to them.
The big problem with "blocking ads is unethical" is that it presumes that the relationship between the website and client is covered by some sort of contract. It absolutely is not. Far too many people think they can unilaterally generate a contract of adhesion[3] and then proceed as if it was agreed to simply because they wish it was so or they listed some fine print in the ToS/etc.
Bonus: I don't think the people who push this kind of "pseudo-contract by ultimatum" have really thought about the full mutually-assured-destruction consequences of this kind of scam becoming acceptable to society. Imagine this HTTP header, which has the advantage of being presented before the transaction has been completed, which leaves the server free to decline the offer:
Would the "content producers" like it if that was enforcable? How about the reverse: mandating zero-cost for a subscription site? If you think this is ridiculous: good - it is ridiculous. Just like when the advertisers do it.