a) Blue, gingham check shirts have been around for many, many, many years from many different manufacturers. I've had similar gingham check shirts from Land's End and Hilditch & Key, who are two very different firms at two quite different price points. Simply because a firm makes a blue, gingham check shirt doesn't mean that they're ripping off another firm.
b) They're made from different fabric - the J.Crew one is (by the look of it) poplin, the Gustin one is flannel. So, one's more of a summer shirt, one's more of a winter shirt.
Also, less importantly:
c) I can't believe that J.Crew is charging that much for a very average shirt, regardless of cloth. What the heck? Are there people out there who will pay that much for a J.Crew shirt???
d) I really dislike this part of the J.Crew sales blurb: "...this shirt is finished with bespoke-inspired details like genuine mother-of-pearl buttons..." Oh, really? How amazing. Perhaps next they'll start mentioning that it has special details like a collar or sleeves because bespoke shirts also have those things.
I hold no brief for the J. Crew shirts, but you need to tighten up your snark.
Lots of shirts have plastic buttons, so the "collar or sleeves" analogy doesn't really hold up . . .