OP, 'rough cubes' & 'pellets' could mean anything, so you need to tell us what you're talking about there. I strongly disagree with your x-owner about sweetfeed being healthy - as healthy as eating Maccas every day perhaps! I suggest you do a bit of study into equine digestion & nutrition, to learn what's needed, what's good & bad.
My belief is that I'd rather spend the money up front on good feed (and other preventative care like feet, teeth, vax and worming) than down the road on health issues and colic or laminitis.
Agree. I wouldn't consider a product with these top ingredients(Wheat middlings, ground soybean hulls, cane molasses, ground corn, wheat flour) a good one though.
IME you also tend to get what you pay for & something that's expensive per bag may well be the most economical by providing your horse with good nutrition & needing to be fed at a lot lower amount than 'cheaper' ones.
Basically for a normal, garden variety horse, what I'd consider a good basic diet is grass/hay free choice or little & often and *appropriate* nutritional supplementation. I would only feed something for extra energy if the horse needed more 'groceries' and I would generally avoid grainy, starchy, sugary feeds. As for 'taylor made' feeds, I would also tend to avoid products without fixed ingredients, such as (most?) Purina & Nutrena feeds, and avoid products full of 'middlings' & 'product', as this means the byproducts or sweepings.
...Oh & Absit, are you talking about a 1 terabyte scoop or a 1 thoroughbred scoop??