Not nearly inedible, just not commercially practical for the effort versus the amount of meat inside. I prefer their taste over the commercially sold reds, they are sweeter in a wider range of seasons. Purple uni crushed up with soy sauce is the perfect sauce for sheephead sashimi.

Spread this information to any sushi chefs you know. The opportunity to help sustainable fisheries by eating puple urchins into obscurity is huge. It's what our economic system is best at.

By "inedible" I didn't mean that purple urchins taste bad necessarily (acquired taste). It's just that shelling them takes so much work that it's not worth the effort for chefs. There are millions and millions all along the coast; convincing a few people to eat them won't make a dent in the population.

That's what we thought about abalone, dodos, passenger pigeons and buffalo.

Fugu isn't exactly easy to process for eating, but people are willing to pay a LOT of money for the privilege of eating it.

All you need is the right marketing, and purple urchins will be like hen's teeth within 10 years.

Even if there were an increase in demand for the purples you'd still be hard pressed to get them commercially, California has been squeezing the number of licensed commercial boats down to about 100 and the market's flexibility is constrained by that.

Purple Sea urchins are an appreciated "connoisseur" dish in all Southern countries of Europe. They are really, really good in fact, with a fine flavour and soft taste, but only when in season, when they feed on the appropriate algae and when taken from a clean source.