horses don't care one iota about how pretty the stalls are, how well groomed the staff is, that the riding ring cost $200k to build. To most horses, being allowed outside all the time, to roll in the mud, to run and buck and fart whenever they feel like it, is a HUGE increase in the "standard of care" over being pampered in a 12 in 12 out situation. You can get crappy hay fed at high end boarding barns. You can get feed fed that is high in sugars at high end boarding barns. Boarding doesn't increase the standard of care any more than at home decreases it.
If moving your horses home includes a drastic change in the standard and complexity of horse care and a significant reduction in horse/barn amenities, yes, obviously you are going to save money, just as if you moved your horse from stall board at a fancy facility to pasture board at a more simple place. The savings is not in having your horses at home, it is in the simplification of their care wherever it is.
People are quite capable in many cases of giving their horse as good or better care at home AND spending less money to do it.
Interestingly, I have had several fairly particular clients over the years who have ended up buying their own horse properties and moving their horses home and in each case their standards relaxed dramatically. It takes a lot of work to keep stalls clean, buckets fresh, blankets changed, fences fixed, arena groomed, aisle swept, etc, and when people realize exactly how much work, they often decide to drastically simplify things.
OR, you can set up your home environment such that it doesn't involve as much hands-on work, still maintain a very high standard of care *as far as the horse is concerned*, and save quite a bit.
Neither situation is right for every person.