Mineral Purchase Pricing (ORRI) in Eddy County T18S R29E

In some ways, this is a repost of post back in February. I have since gotten a better handle on our interest so can ask more pointed questions. My family (four siblings) own about 20 net royalty acres (NRA) of override royalty interest (ORRI) in the north half (N/2) of Section 28 of T18S-R29E. In addition, I am confident that we own some ORRI in the S/2 as well, though I am still determining how many net royalty acres. I’d love any and all opinions as to what this interest might bring (expressed as $/NRA) if sold in current market conditions. We recently received unsolicited fishing letter offers of $3500/NRA and $6000/NRA for the N/2 interest. Has anyone sold or received offers recently in this area? Again, our interest is an ORRI, so we can’t lease it. Thanks.