Here’s an excellent historical source about grazing fees in the early 90’s.
There was a great deal of kerfluffle between the envirals and ranching interests when Clinton appointees Bruce Babbit and Jim Baca started proposing grazing reforms, pretty much renewing the Sagebrush Rebellion.
1993 seems to have seen a doubling of the fees, which may have been one of the reasons Bundy decided to quit paying
You can search High Country News archives on grazing reform back then. https://www.hcn.org/@@search?b_start:int=10&SearchableText=grazing%20reform
The fees have been the same since 1986. The law in 1986 set the minimum fee at $1.35 per AUM, and the fee for 2014 is still $1.35/AUM.
It takes an act of congress to raise the fee amount. They haven't.
From the BLM's website: "The Federal grazing fee, which applies to Federal lands in 16 Western states on public lands managed by the BLM and the U.S. Forest Service, is adjusted annually and is calculated by using a formula originally set by Congress in the Public Rangelands Improvement Act of 1978. Under this formula, as modified and extended by a presidential Executive Order issued in 1986, the grazing fee cannot fall below $1.35 per animal unit month (AUM); also, any fee increase or decrease cannot exceed 25 percent of the previous year’s level. (An AUM is the amount of forage needed to sustain one cow and her calf, one horse, or five sheep or goats for a month.) The grazing fee for 2014 is $1.35 per AUM, the same level as it was in 2013."
My comment = since it cannot fall below $1.35/AUM per the 1986 executive order, and the rate in 2014 is $1.35/AUM, I'm thinking there was no raising of fees in the interim. There may have been, but it's been at the floor of $1.35 for several years now.