I think boarding has always been a difficult business, but - as illustrated very well by mvp above - there is a very challenging dynamic that includes rising costs for land and infrastructure as well as perhaps different client expectations now as well.
In any case, though, the basic rules of supply and demand apply to this business just as they do to others, particularly for those that revolve around the way people spend discretionary income.
In my area, boarding at a facility that offers nice facilities and good care run by competent professional horsemen will run at least $1000/mo. There are very, very few that allow boarding only (without lessons/training packages.) That is simply the market rate for a place with certain amenities (turnout, indoor, excellent footing, etc.)
I haven’t owned horse property in this area so it’s hard for me to say for sure whether or not that is a profitable rate for the owners of those facilities. Given the dearth of boarding-only options, though, I am guessing that the margins are quite slim, and are thus bolstered by the requirement for lessons and training that most barns insist upon. With respect to the question posed above:
I have been told the way a barn makes its money is through training and selling horses. But let me get this straight : I have to take the money I make from training and selling horses in order to buy a new indoor arena for the clients that pay essentially nothing?
I can understand why you would see the situation that way, but I’d encourage you to also consider whether or not that indoor is an amenity that is expected or required in your market in order to attract clients who will pay for not only boarding, but also sales and training services. If you lose money on your boarding only clients, perhaps consider not offering boarding as a stand alone service, as so many other barns have done. Unless you are using boarding income as a cash flow device - and many do it to help with the expense of personally owned horses, or to help justify infrastructure they want but could not justify for only their personal needs - then running a service that generates no revenue is a tough one to persist with.
Of course, the other aspect to consider when addressing pricing is that key component of what the market will (can) bear. If you raise your prices to the point that the pool of potential customers is too small to support your business, that is obviously going to be a problem as well. (And the reality is that there are areas where certain types of facilities are perhaps simply not viable for that reason.)