What makes marbled steak so tasty is the fat, which yes, can increase BP and cholesterol, but hey I agree YOLO is the rule. If i go of a heart attack, i hope it is relatively quick, even if excruciatingly painful. Just be conscious of how often you eat like this and work out more the next day to burn it or use it up.
Consumers often can't find marbled steak in regular groceries. Butcher shops are better and give you more control over the meat. It's the fine marbling that you can't get in the chains, which is genetic and really characteristic of the cattle breed and quality as well as what they eat. It will cost more for better steak, no doubt about it. I went to Japan once, and even their regular beef looked so amazing, i thought it was fake until i went up close to inspect it.
Aging helps, but it is controlled rotting. I try not to think about that, but that's what 30-day aging does - rots away the steak, probably end up with only half the meat that you started with. Gross, but tastes good though and the protein and enzymes have really broken down to tenderize the sucker