The difference is, since it is a web comic you already KNOW you will like it, you already know how you value the content. With Toms offering you are taking a bit of a gamble on just what the value of the content will end up being. So we are left with Tom needing to spend time establishing his story telling credentials just so he can take a shot a publishing a series of short stories? Guys that do web comics tend to dedicate hours upon hours a week to get things up and running, for months or years before publishing a collection is a practical reality.
How do you know people won't buy it? In the last 30 days people donated € 152. That's not much, but it's something. And no, I'm not saying spend that. I'm saying that at the minimum there are people who probably wouldn't mind buying a book to support the game. I know I've donated before, and rather than a title that lasts for a bit and an extra drone, I'd actually have a physical, tangible object. That'd be awesometastical. Even better if there was a signed copy (yes, I'd prolly splurge and buy that instead of the regular one).
You could always just ask people if they'd like it. There are ~400 active daily players of BM (pulled from BM stats), another ~300 on top of that that consistently log in atleast every few days. That's ~700 people you can ask whether or not they'd like something. You could even ask them how much they'd expect to pay for something.
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