Hello! My guess is that the two firms making the offers are banking that there will be a new well drilled, or possibly they can sell it for more than they are offering to buy it from you. San Augustine is an actively drilled county - we recently had several allocation wells drilled in San Augustine in the Haynesville/Bossier. So I would not sell without thorough research and understanding of my mineral interests.
But I am curious as to how it can be, that you would be paying more in taxes (severance? ad valorem?) than you make in royalties? That would indicate a problem, as taxes are just a percentage of the gross royalty you receive.