I think you might be surprised what people would be willing to pay. Especially if it was their son's or daughter's first animal. Hell, it would make a great christmas or birthday present every year to engrave the cases with the hunt information on it for each big game animal killed. I wouldn't think twice about $25 for something like this to give to my kids for their successful hunts. But at $5 each I might even do this for myself lol.I do understand that, and for most items I charge substantially more. However, I don't know many people who would pay $25 to have done what they're already doing with a sharpie.
I would put this more into marketing than sales. Like handing out pens with a logo on them.