Refers to a major upswing in market prices, especially in stocks. Often used in economic news.
A boom has come to IT-related stocks.
After a boom, a reactionary decline is a concern.
暴騰 means 'sharp rise' or 'soaring prices', focusing on the rapid increase, whereas 大相場 emphasizes the overall booming market condition.
Compound of 大 (large) and 相場 (market price). The exact historical derivation is uncertain, but the term is conventionally associated with financial booms.