The same can be said about any food. A steak is a steak be it from the grossly overrated Ruth Chris's or the almost always outstanding
Del Frisco's or
Charley's. With enough effort and care, and careful purchase of the meat, it can be done at home on an appropriate grill. But the total experience of the meal and accompanying sides makes the trip and cost of Charley's worth it.
Same with In-N-Out. The consistency, the sides, the options of the "secret menu" and special sauce make it one of a kind. In this case not expensive - quite the reverse - but an experience in fun dining that places like Disney try to recreate - at inflated prices - and fail miserably. They do that because people want that old time service and quality but in Disney's case they are the exact opposite. Places like In-N-Out are truly unique establishments that have built a cult following that appreciates the difference from a mass produced, frozen production line meant to maximize output at the expense of any real flavor vs a home made, quality controlled simple burger done as it was meant to be.
It is not a culinary breakthrough but a simple idea from mid-century 1900's that got lost by most eateries. Worth the trip if just to recall (or learn) how they did it "back then". If all you want is a house burger hop on over to Ralph's, get some ground beef or ground round, buy a package of manufactured buns and maybe a premade bag of salad and toss it on the grill most timeshares offer. I prefer a great home made burger on a fresh made bun with incredible fries and maybe a shake for under $10 any day. YMMV.