The phrase "to buy up" means to purchase or acquire a large amount of something, typically goods or assets. It can also refer to buying out all available stocks or shares in a company or market. The term is often used when there's an increase in demand for a particular product or service, causing prices to rise as suppliers seek to take advantage of the situation by selling their products at higher costs. In this context, "to buy up" means to purchase everything that is available on the market, regardless of the cost.