I recommend getting ahold of Harrison and Mecklenburg, Inc. They are a local attorney firm that has been in the area for a long time and represented mineral owners for leasing and sales of their minerals for a long time. They will be more in tune with current prices and buyers.
Harrison & Mecklenburg, Inc:
202 N 6th St
Kingfisher, OK 73750
Worth a call for sure even if you don't use them, they can help educate a little more in the activity price and well results.
Did Sandstone happen to mention Devon filing the corporation commission activity for a new HZ well on your minerals in the last few weeks? If not, you might remind them about Croslin V. Enerlex, Oklahoma Supreme Court Case # 109786