There are so many variables in production agriculture that make it difficult to answer the OPs question, but I'll take a stab at it. The quality of the hay dictates its value, coupled with the local supply/demand ratio, which can vary greatly year to year, and even within a year depending upon the weather (drought). Rolls of high quality coastal are bringing $125 + in and around San Antonio area. It used to be standard for a landowner to get 1/2 the crop, but that's negotiable, along with who pays for the fertilizer and weed control.
Everything's negotiable, and can be adjusted year to year. The more involved you are with the expenses (it can be a large investment in money, time, and risk) the more entitled you will be to a larger % of the total. You might make a lot one year, then lose it all back the next. It's difficult to make a profit long term without close management. Good luck!