That is literally what patents were invented for. Give the entity that puts the resources into creating something new some protection to be able to recoup that
Also, not all patents are monetizable.
Then they hope they can sell it at a profit.
Products becoming cheaper is a result of the processes getting more optimized ( on the production side and the supply side ) which is a function of the desire to increase the profit on a product.
Without any other player in the market this means the profit a company makes on that product increases over time.
With other players in that market that underprice your product it means that you have to reinvest parts of your profit into making the product cheaper ( or better ) for the consumer.