From reading this board it appears that a lot of folks in other parts of the country tarp their hay. Here in Texas nobody does. That’s not to say you don’t have some loss, it’s just that in this part of the country the time/expense/effort to tarp is not justified. Sure, if you have a hay shed, use it. If you don’t, don’t worry about it.
The outside of the roll will get to looking old but the damage from weather will penetrate less than an inch. On the bottom of the bale you will loose over an inch. When you open the roll the hay under the surface will be clean and bright. Yes, there is some nutritional loss in carryover hay, so don’t pay new hay prices. But as long as you are keeping salt and mineral out, and supplementing with cake or cubes through the winter, your stock will do fine on year-old hay.
As far as prices go, it depends on what part of C-TX you’re in. Rain has been very spotty. If your area made good hay this year you will be able to dock hard for last year’s hay. If not, it will bring closer to new prices. Just make sure you’re not buying hay that’s been in the field for years.