> those big bales rolled up are quite heavy - and expensive
Depends what you mean by "expensive". You can get one typically for $15 - $50 / bale. Here's a website: https://allhay.com/
Prices are much higher due to the fertilizer and fuel prices. Around me It's going for $50-$55 for a 4x5ft bale (a few years ago it was $20 / bale).
That said, those can weigh quite a bit, a 4x5ft bale will be 800 - 1200 lbs depending on moisture content and field composition. A cow will eat 20-40lbs of food a hay, depending on weather (they eat less in severe cold or heat).
That equates to a single bale lasting one cow a approximately month or in reality, a heard of 30 cows needing about one bale a day.
Using today's price of $50/bale, that's $1.67/day per cow to feed (a couple years ago it was much lower, say $0.5 - $0.75).
Given it takes 2-3 years to maximize beef production AND assuming you only need feed half the year (grass fed cattle often graze), we're talking ~$750 to feed over the 2.5 year average (assuming 2.5 years @ 180 days).
In terms of meat, you're probably going to get somewhere around 450lbs of use-able meat. You have to pay a butchering fee on that as well. That's probably $700. You'll also have transportation, fees, etc (let's just say $200/head). Total you're looking at a cost of $3.67/lb of processed beef. You can then resell for $5-6/lb right now to a reseller. This is a net of around $675.
If you feed grain, you can effectively expect the same thing, but:
1. Grain fed will typically be cheaper per lb.
2. Grain will create a more tender meat (it's why people finish with grain)
3. Cows fed grain gain weight, so profit can be somewhat higher (often offset by organic nature of many grass fed cows)
4. Grain-fed tastes better to most people