Too much information is missing.
Do you have horse(s) in any way troubled with metabolic problems? These would be things like previous laminitis / founder, Insulin Resistance PSSM, etc.
If you have any horses with metabolic problems, present or past, you must stay away from grains with starch or sugar and stick to feed ingredients like beet pulp, alfalfa pellets, fat supplements or protein supplements like soybean meal. Older horse particularly benefit from soybean meal.
If you have no horses with metabolic problems, then grain or grain products are the most reasonably priced and do the most good to keep horses in good condition.
We have 50 horses and have 1 that we restrict grain products to. We have about 25-30 that get no grain at all. We have a few that only get grain when we bring them in to ride or work with. Our grain is rolled corn based with Wheat Midd pellets. It contains soybean meal, a calcium supplement and a vitamin A-D-E premix. We pay $244.00 a ton for it in bulk. That works out to $6.10 per 50#. So, feeding a concentrate does not have to be expensive. The most any of our horses get is 4-5# per day and these are the old horses and the poor keepers that we have. We have a number of horses over 20. Five pounds of this feed works out to $.61 per day. Most get either no grain or up to $.20 a day for grain. They all get free choice grass hay.
So, there are a lot of variables that you have to figure out. You have to be a good enough manager to know what your horses can and cannot tolerate in order to manage them correctly and not throw away a lot of unnecessary money. Feeding only 'safe' feeds would actually be like throwing a lot of money away if you have horses that do not have metabolic problems. On the other hand, if you cannot figure out what they can tolerate, then it would still be safer than a more efficient feeding program. That is what good horse management is all about.