THE NATIONALS wouldn’t be playing baseball in Washington today, much less pursuing a spot in the playoffs, if not for $611 million from the District government, whose elected officials had the courage to go to bat for the controversial investment in a stadium for the team. So it’s beyond belief — cheesy is one word that comes to mind — that the owners of the Nationals are refusing to pay what amounts to a token amount of money to ensure the late-night Metro service that will be essential to the team’s fans in October.

With the postseason and its prospect of later games just two weeks away, the Lerner family seems dug in with its refusal to pick up the extra costs of running subway service past midnight. The issue, as The Post’s Mark Berman reported, came into focus last month after a Metro closing left hundreds of fans in the lurch after a rain-delayed, 13-inning win that ended after midnight. The team subsequently asked the city to pay the costs of any future late Metro service, a request rebuffed by the District and rejected by Metro. A statement issued by the team said “a number of parties” are involved in discussions and “all options” are being looked at.

Here’s an idea: How about the Nationals follow the example of every other owner of a sports team in the region, as well as organizers of other big events, and accept Metro’s reasonable rules. That means putting down a deposit of $29,500 to prevent an interruption of service. In the event of a late game, most of the money probably would be recouped through increased ridership; but even if it is not, that’s a modest amount to pay for fan convenience during (we hope) the first baseball playoff games in Washington since 1933.

“Can you imagine a situation where the Nationals are tied in the ninth inning and all of a sudden people are exiting out of the facilities to make it home because of the Metro? That would be a nightmare,” is how Nationals fan Lewis Lowe described the alternative to The Post. D.C. Council member Jack Evans (D-Ward 2) says it won’t come to that; he says a solution is in the works that would guarantee that Metro stays open late. He didn’t specify where the money would come from, but we hope the city isn’t thinking about caving in. If it does, it shouldn’t be surprised if the Capitals and the Redskins come looking for a similar handout.

The District has already gone to extraordinary lengths to accommodate the Nationals; in addition to coming up with the money to build the stadium, it shares in the cost of providing extra police protection and assists in traffic management. No question the city gets a return — fans from across the region stream to the stadium, giving new life and revenue to the District. But the Nationals would do well not to bite the hands that feed them — both at the Wilson Building and in the stands.