Lets pretend that all production is contingent on fixed cost capital, the good or service made from this capital is sold at a price that means that demand is below what the capital has the capacity to produce, lets say we have a theatre with 10 seats and the market price is \$2 which puts demand at 5 units. By lowering price the demand for the service increases which partially off sets the revenue lost from lowering price, lets say lowering the price to \$1 increased demand to 9 units. Here the seller has gone from making 10 dollars from selling 5 units for \$2 each, to making \$9 from selling 9 units for \$1 each. The seller has lost \$1 for lowering price, but the buyers have made approximately \$7. Since the 5 buyers who would've bought for \$2 now pay \$1 saving \$5 collectively. And the 4 new buyers, who value the product somewhere between 1-2 dollars would have valued it on average 1.5 dollars which makes them a 5o cent surplus each, or \$2 collectively.
So if the government pays the cinema to lower prices to \$1, they spent \$1 but increased the buyers consumer surplus by 7\$. This is a solution for the underutilization of capital that we see in the free market, empty seats on buses and trains, empty roads, empty theatres, empty stadiums, games unplayed, films unwatched, online courses unlearnt from, medicinal and technological innovations unused, etc.
Even when the production process isn't very capital intensive that need to profiteer off of the fixed capital makes the price arbitrarily high which scares away consumption.