«بِعْتُكَ هَذَا عَلَى أَلْفٍ»
“I sold you this for a thousand.”
A sale involves the exchange of property against a price. Ala can accordingly function like the particle baa in expressing compensation, rather than a physical relation of being “above” the money.
The transactional context establishes the relationship of consideration. Similar contextual reasoning can apply to comparable contractual language.