Its a friend's place, which makes it very cost effective, although its possible to rent houses on the North Shore for very reasonable amounts of money (I'm talking about the North Shore of Lake Superior - you won't be sunning yourself on a sandy beach or playing in the waves - even in August you may sun yourself, but the beach will be big river rocks. However, its amazingly beautiful, with waterfalls every couple of miles cascading into the lake, rocks to scramble over next to the water, huge ore boats floating by once in a while. We've seen a bear and her cub out the house window (kept the kids in for a few hours after that).)
You can do similar things with Disney - renting a very reasonable house offsite. But with Disney there is no way around park tickets no matter how reasonable you find a house to share. With the beach, for us, the attraction is the nature. Whether the North Shore or Hawaii or Mexico or Hilton Head (all beaches we've been to in the past five years - except for Hawaii, all cheaper than WDW), the beach involves watching the water, walking or hiking near the beach, swimming (not at the North Shore). Hawaii was expensive - airfare was expensive, food was expensive, and we did things like take surf lessons and go whale watching.
Also, most places in the U.S. have a beach nearby. If the only beach under consideration is the Jersey Shore, I completely understand why its so expensive. But if you live in Minnesota or Wisconsin and the beach is a lake cabin owned by family or friends - it isn't very expensive at all.