Round bales you are asking about are probably the large 5'wide x6' bales that require a forklift or other special means to handle. They typically weigh 1200 pounds if baled from fescue, brogham or...
It would depend on what type of hay how much it would cost, also whether it was a small square, a large square, a soft core bale or a hardcore bale. Small square weigh between 75 & 100 lbs, large...
There are generally two types of hay bales. With quite different weights. The most common ones that people buy at feed stores or the farmer, and can be moved by one person, are the type you may have...