I don't mean junk as in quality, I mean junk as in not really useable. Buckets pile up at dealerships all the time because they don't fit anything current and its costly to refit them.
As for quality differences amount buckets.. like anything you get what you pay for. Steel is expensive, more steel = better buckets.
The link to that Kubota bucket... don't buy that. That's long term parts support, things are pricy there because they keep that stuff on a shelf for years to support product. If you go to the sales dept for something for a more current model it would be half that. For example, the 60" QA material bucket for the current B-series tractors lists under $600.