Consider what happens when you explore: either you find something new, or you reclaim something abandoned or inaccessible. Merchants can't trade with Fartown because the mountain pass has been closed for a century by horrific beasts; the local noble wishes he could reclaim one of his villas; the rugged hills contain a gold vein. By clearing the pass in some way, reclaiming the vista, or discovering the gold vein, you create value, much as you would if you found a lost treasure. You don't get that value unless you either exploit the value yourself or pass that value on to someone else who can exploit it.
If adventurers exploit the treasure themselves (create a trade caravan, build a toll road and man outposts, rebuild and operate the villa, excavate a mine,) then they get xp for the money earned. Trade is easy, since you can just use the standard 1 coin = 1 xp exchange rate for any net income. Structures, like the villa, have a treasure value equal to what it cost to build them originally, minus any building expenses needed to make the structure usable (don't deduct improvements, though.) Other areas add income from the primary economic activities (winemaking, logging, fur trapping area) appropriate for the area's resources.
If adventurers report back information about a new or reclaimed resource to someone able to exploit it, guess the max value of a limited resource or the income for one year of trade or other renewable resource and give the adventurers 1/10 the gp value in xp.
Sample Economic Estimates:
- Trade: Use the appropriate subtype of Treasure Type A (gold only.)
- Renewable Resource: barony tax income, minus expenses and labor, with max laborers = total Charisma scores of PCs.
- Gold Mine: Treasure Type G (gold only.) Use gems only instead for a gem mine, add jewelry value if you hire jewelers.