Spyglass of Finding: slotless item, +10 Spot (competence), continuous Darkvision, continuous See Invisibility = 59,000 gc.
Adding True Seeing per the "gem of seeing" (30 min of use/day) brings the total cost to 119,000 gc.
DM, will those effects work at spyglass range?
The math:
See Invisibility = 2000*(SL 2)*(CL 3)*(1.5 duration factor)*(2 slotless)*(1 stacking factor) = 36,000
Darkvision = 2000*(SL 2)*(CL 3)*(1 duration factor)*(2 slotless)*(0.75 stacking factor) = 18,000
Spot bonus = 100*(Bonus
2)*(0.5 stacking factor) = 5,000
Stacking factor shifts once you add True Seeing:
Gem of Seeing = 75,000*(1 stacking factor) = 75,000
See Invisibility = 2000*(SL 2)*(CL 3)*(1.5 duration factor)*(2 slotless)*(0.75 stacking factor) = 27,000
Darkvision = 2000*(SL 2)*(CL 3)*(1 duration factor)*(2 slotless)*(0.5 stacking factor) = 12,000
Spot bonus = 100*(Bonus
2)*(0.5 stacking factor) = 5,000
Stacking factor assumes the abilities qualify as being "similar."