The possible reason I can think of why it is mentioned that the storehouse contained spices and olive oil along with valuable treasures like silver & gold is that they were holy and kept in large reserves for use in the temple.
- Olive oil and spices are ingredients used in the holy incense offering in the temple.
- All the Temple Items were sanctified with oil and spices.
- The menorah in the temple uses olive oil
- Also the Olive Oil was used for anointing priests and kings.
Please see the below verses for above points
Exodus 25:6 olive oil for the light; spices for the anointing oil and for the fragrant incense;
Exodus 30:22 Then the Lord said to Moses, 23 “Take the following fine spices: 500 shekels[d] of liquid myrrh, half as much (that is, 250 shekels) of fragrant cinnamon, 250 shekels[e] of fragrant calamus, 24 500 shekels of cassia—all according to the sanctuary shekel—and a hin[f] of olive oil. 25 Make these into a sacred anointing oil, a fragrant blend, the work of a perfumer. It will be the sacred anointing oil.
Exodus 25:26 Then use it to anoint the tent of meeting, the ark of the covenant law, 27 the table and all its articles, the lampstand and its accessories, the altar of incense, 28 the altar of burnt offering and all its utensils, and the basin with its stand. 29 You shall consecrate them so they will be most holy, and whatever touches them will be holy.
Exodus 30:34 Then the Lord said to Moses, “Take fragrant spices—gum resin, onycha and galbanum—and pure frankincense, all in equal amounts, 35 and make a fragrant blend of incense, the work of a perfumer. It is to be salted and pure and sacred.