I have to say, I've found our WDW trips to be cheaper (per day) than many other trips we price out. That is why we never really get anywhere else. We start out planning to go somewhere else and then always revert back to WDW to keep it in our budget. Actually, I think the price of our honeymoon in Jamaica 20 years ago was more than our last WDW trip.
Obviously, a lot of this has to do with what we want / like to do, where we live, and when we can travel. This years plan looks like this:
I am currently trying to plan a 5 night trip to Boston so my DD can visit a college there and take a 4 day music program they are offering. Even when not counting the cost for the music program and even though DH will not be coming along, it will cost us as much as our average 7 night WDW trip for 4. So, more per day, per person.
Next up, Nashville. Again, for a college visit and then a few days of tourist stuff. This may be slightly cheaper per day, but not by much and I'm guessing it will be a little less fun than WDW

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So Cal and
Disneyland. Yeah, this is going to be a small fortune. I have tried to do this a few times, and could never bring myself to spend the money. Again we will be visiting colleges (at least 3) so, I guess I will bite the bullet.
We have gone to the Dells a bunch of times and that is always a lot more per day than WDW. We go for less days, so it is "cheaper", but per day, it is still more despite being so close to home. Also have priced out Cedar Point and Kings Island a few times over the years. If I recall it was more than the Dells, and why we didn't go.
We've been to St Louis and it was ok, but not significantly cheaper and much more of a "soaking up the atmosphere" kind of trip. Not a ton of activities. So, I would still say WDW got us more bang for our buck.
DH has done weekends to a few places with his Dad and brothers to see MLB games, etc. Has always cost more per person per day, because it is a short trip and they spend a lot of money at the game and at the bar!
I keep seeing people mention DC. It sounds terribly boring to me (live just outside Chicago and I don't enjoy our museums and such either) but I may have to give this a shot. My older DD and DH are big history buffs and have a lot of interest in politics, etc. They might like it. Younger DD and I will have to find ways to entertain each other. lol.
The beach and cruising is not for us and camping is a NEVER!!!! Wish those were of interest. It sounds like those are all more budget friendly.