A couple of things I have not seen mentioned; weather aside, quality and quantity is relative to a couple of things. Soil quality, fertilizer, overseeding or a total rebuild. These additional costs must be factored into what you currently have. What kind of grass is there? Typically, timouthy or orchard perhaps alfafa (a legume) or a mix. Some customers will prefer or demand one over the other, some not so much.
Then there is the weather. I moved out of PA in Feb 08'. Up until then, the last say six years had been seen wet conditiions going into dry making the first crop difficult if not impossible to get even close to right time wise then zip after that. This past year had to be horrible?
Hay comes in with a narrow window of a week or so and maybe three dry days to cut, dry, bale up and remove. Any rain at all usually means "horse quality" is out.
You can make the first cut and windrow and a follow up tedder yourself. Baleing is going to require more people and/or more equipment. You can do it with one person on the wagon stacking hay but two is better. Or, you can invest in all kinds of equipment to automate the process and lessen your need for help. Even rounds go better with at least two operators and two tractors.
Some of the larger (for my area) hay suppliers literally bust their backside during the hay seasons. They need to have extra help on hand (often not so dependable in spite of a bad job market) and it is a race to get the crop up and in the barn.
After shoulder surgery, I paid an extra buck a bale to have it delivered and stacked in my loft. I also negotiated filling my barn and paying as I could. In that manner, my supplier did not have to stack it in his barn and then move it again. You may negotiate going directly to a customers barn. On credit like I do, you could get taken over.
In my area, the average deal is a 50/50 split. Say I have the hay, you have the manpower and equipment. You come in and bale it all, take your share and go. I then either deal with my cut myself or further negotiate for some help putting my share up. Field maintenance or improvements are negotiated.
IMHO, a field free for the taking is no bargain for someone not already in the agricultural business unless disposable income is not an issue. My supplier also has a number of horses and owns plenty of land. He also has adjoining acreage he cuts for others. He has a full time more or less unrelated business to attend to. I never asked him directly but I suspect he does not sit down and look at his overall bottom line.
Lastly, one influence that applies in many areas with hay crops. There are a lot of cash deals going on.