Assuming 1,750 acres . . . . .
$3,500 was $2 an acre.
$13,000 would be
$7.43 an acre.
Now, you may have just somewhat
"made the case" regarding what I've been alluding.
What age is your "FIL"?
You need not answer, as we'll just assume he's a lot older than you
My point is, I suspect he could easily pay $7.43 an acre for this lease,
but he's "in the know", and knows it's not worth it.
Besides,
he has plenty of other places to hunt for a lot less or "free".
Just saying, the dynamics are constantly changing.
Ultimately, price reflects value, but prices can be way low or way high throughout time.
Someone besides your FIL may lease that for $7.43 an acre,
but fair chance they'll let it go after 1 year.
The next year, it may get leased to someone else for a lower price than $7.43.
Or might be $10.
Only time will tell.
I just know your FIL isn't going to be a poor steward of his money,
and neither am I.
It will be up to the next generation to squander the family's fortune