KC Royals Star Eric Hosmer -- Epic Post-Game Bar Tab ... Was Five Figures!

The massive Kansas City Royals victory party funded by first baseman Eric Hosmer was no cheap night on the town ... TMZ Sports has learned his tab for the night was more than $20,000!!!

By now you've heard of Hosmer's exploits ... throwing down his credit card to foot the bill for a one-hour open bar at McFadden's in Kansas City following the team's epic win over the Los Angeles Angels.

With the bar packed with overjoyed Royals fans, the GM of McFadden's tells TMZ Sports that Hosmer's bill was around $20k!!

As part of the celebration, Hosmer ordered some Ace of Spades and Veuve Clicquot Brut Yellow Label champagne for himself and a few teammates, which he graciously shared with some fans ... well, he sprayed them with it anyway.

If there's any fan base that deserves it, it's the Royals (sorry Pirates fans, you'll have your chance someday).