Map Modifiers and Crafting
Maps themselves are items and can be modified with currency:

Transmutation/Alchemy Orbs: Add magic/rare mods.

Vaal Orbs: Corrupt maps for powerful modifiers (but with risk).

Chisels: Improve map quality (which increases item quantity).

Sextants: Add special modifiers to POE currency regions of the Atlas.

Scarabs: Add league mechanics or boosts to buy POE2 Currency specific maps.

Carefully crafting your maps ensures you're getting the most value out of each run. For example, a fully chiseled, rare, sextanted, scarab-loaded T16 map can be a goldmine of loot and experience.