overbuy

verb

to buy in excessive amounts

Wiktionary

verb

Etymology: Etymology tree Proto-Indo-European *úp Proto-Indo-European *-er Proto-Indo-European *upér Proto-Germanic *uber Old English ofer- Middle English over- English over- English buy English overbuy From over- + buy.

To buy excessively, especially to buy more than one needs or can afford.
To buy at an inflated price.