Agreed, its not like the designer was doing some sort of high-detail pixel art or anything. Favicons can take a really long time. They are an art.
However, this one is not even that good of a job. Its a little off center, the font isn't very clear, hard to read. Clearly just a photoshop resize job. I would expect much cleaner work for that price
Is it possible the £585 is a standard fee regardless of simplicity or complexity? i.e. oil change, $40. (no matter it's an easy access filter or complicated filter change)
However, this one is not even that good of a job. Its a little off center, the font isn't very clear, hard to read. Clearly just a photoshop resize job. I would expect much cleaner work for that price