When there is a seller's market for a particular product, there are fewer of the products for sale than people who want to buy them, so buyers have little choice and prices go up. Compare buyer's market.
[business]
seller's market in British English
a market characterized by excess demand and thus favourable to sellers
See full dictionary entry for market
sellers' market in British English
noun
a market in which demand exceeds supply and sellers can influence prices
seller's market in American English
a state of trade favorable to the seller, with relatively great demand and high prices of something for sale