Floyd Mayweather and Conor McGregor gave fans in Las Vegas a fight worth watching, but the biggest winner of the night was the arena around them.

T-Mobile Arena has been open for more than a year, has hosted numerous concerts, fights and other events and, this fall, will host Las Vegas’ new National Hockey League team, the Golden Knights. Even though it was about 6,000 shy of capacity for the Mayweather-McGregor fight, it still commanded $10,000 for ringside seats. What did the citizens of Las Vegas and surrounding Clark County pay for this privilege? Absolutely nothing.

Unlike the new football stadium that Las Vegas is using to lure the Oakland Raiders to Sin City in 2020, T-Mobile TMUS, -1.06% doesn’t touch hotel taxes that could have been redirected elsewhere. Unlike the $750 million tax payout that Raiders owner Mark Davis pried out of Clark County politicians with help from casino mogul and now-spurned business partner Sheldon Adelson, T-Mobile’s $375 million costs were paid by MGM Grand (which already operates the Grand Garden arena in town) and sports conglomerate Anschutz Entertainment Group.

This isn’t only a rare occurrence in sports business, but a near-miracle when it comes to building an arena. The Detroit Red Wings of the NHL and Detroit Pistons of the National Basketball Association will also be getting a new arena this year. However, even with the combined resources of two professional sports franchises, the city of Detroit and its various agencies paid more than $300 million toward the cost of the $650 million facility. Yes, that’s the same Detroit that was billions in debt when it filed for bankruptcy in 2013, whose schools are under an emergency manager and whose taxes are collected by the state of Michigan because it can’t be trusted to do such things itself.

Meanwhile, in Sacramento, former Mayor Kevin Johnson’s administration was so afraid of losing the NBA’s Kings to Seattle that he coughed up nearly $260 million in tax dollars to help fund a $535 million arena, according to Georgia State University’s Sport and Urban Policy Initiative. Just before the arena opened last year, Kings ownership had the audacity to sell the naming rights to credit union Golden 1 — as if any portion of that deal could be described as frugal. They were at least in good company in 2016, as Edmonton shoved $323 million at the $614 million Rogers Place arena and surrounding commercial district.

In 2018, the NBA’s Milwaukee Bucks will replace the nearly 30-year-old Bradley Center with a new arena that covers much of its $524 million cost with $250 million in tax dollars. That includes $90 million in bonds that accrue interest for more than a dozen years before they can be paid off. That interest will add another $170 million to the existing $250 million cost before the whole thing is paid off.

But at least all of the arenas above have tenants. Quebec City’s $310 million Videotron Centre was completed in 2015, with full cost paid with tax money from both Quebec City and the province of Quebec. However, the NHL skipped Quebec during its last round of expansion, as fluctuations in the Canadian dollar have cost the league roughly $200 million in revenue. However, two years of vacancy is nothing compared with the decade of emptiness that the Sprint Center in Kansas City has seen since opening in 2007. One of two arenas in Kansas City — with 44-year-old Kemper Arena being the other one — the Sprint Center has hosted college basketball tournaments and big-league exhibition games. The Nashville Predators, New York Islanders and Pittsburgh Penguins and Los Angeles Clippers all used the building for leverage in their home markets, while Kansas City hotel and rental car taxes are still paying for the $276 million cost of the arena. That adds up to between $10 million and $15 million a year, with only arena owner Anchutz Entertainment Group — the same group that gave Vegas a freebie — dipping into operating revenue.

It isn’t as if teams are clamoring for spots in those empty arenas, either. The NHL is eyeballing expansion into the Pacific Northwest, but Seattle’s ongoing battle over potential arena costs — including those of a current plan to refurbish Key Arena — have set the amount of public money the city is willing to spend on the project at $0.

You may not know it to look at the prices being paid for arenas by some of the cities mentioned above, but Seattle’s actually paying the market rate for a sports facility. Look at San Francisco, for example. The Golden State Warriors will be moving from Oakland to the $1 billion Chase Center in San Francisco in 2019. However, Warriors ownership is financing the project itself, is getting $300 million from J.P. Morgan Chase JPM, -0.21% just to slap its name on the arena and catered to residents’ and officials concerns about traffic and density.

Where Atlanta had to fork over $140 million in tax dollars just to refurbish Phillips Arena and get the NBA’s Hawks to stay and even New York had to pay $300 million just to give the NBA’s Nets and NHL’s Islanders a place to play in Brooklyn, San Francisco and the Warriors got $300 million from Chase seemingly just for existing. Seattle, San Francisco and Las Vegas have shown cities a way forward with arena funding and made clear that you can draw marquee events to your town without having to spend a dime on some team owner’s building.

Granted, each of those cities has spent or will spend plenty of public money on ballparks and football stadiums. However, if you have a city that’s already a destination and that won’t have to strain to keep an arena filled throughout the year, there is no reason to spend tax dollars on an arena that team owners and sponsors can easily pay for themselves.