Are typos worthwhile buying?

Less and less so, every day.
But depends.
I certainly wouldn't base a business model around it, but on the other hand I know some people who made a killing from it, but they were in the door at the very beginning and also (nearly) impossible to replicate. But can't say any-more than than, without breaking confidentiality.
Also not all typos are made the same
1) googel.com.au is an obvious typo.
2) wikipedia.com.au is probably also classified as a typo even though it is spelt correctly (typo being ppl are obviously looking for wikipedia.org/.com).

Also typos largely rely on type-ins. You won't get (m)any traffic from the SEs as all major ones employ spell checkers "Did you mean: google"

Typos like 1) are not worth it, and will likely be challenged or automatically deleted if they are on "the list", 2) are the only ones that may be worth exploring.

Anyway this is just my opinion.

These is no answer to this question. If you just register what you think are good typos you probably won't make much, if you are using data to predict names with traffic you'll do somewhat better. It is an area of the market that is in decline though.

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When you say buying, do you mean buying from someone, or registering ?
I suggest you avoid registering typos because it is unlikley any have been missed by the professional companies that had the opportunity to taste in the past (register and cancel if no traffic )

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