More than half of fans who attended Tyson Fury's recent win over Otto Wallin were given free tickets.
The Brit suffered a huge cut above his right eye in the third round but survived to outpoint the unheralded Swede.
He remains on track for his rematch with Deontay Wilder next February, assuming the world champion beats Luis Ortiz in November.
But of the 8,249 fans in attendance at the T-Mobile Arena earlier this month, 3,898 watched Fury win for free.
The remainder - 3,577 - had paid for their tickets, reports Boxing Scene , with the arena not even half full.
Fury has fought twice in America since signing an £80million, five-fight deal with US broadcaster ESPN.
His second-round win over Tom Schwarz in June attracted a crowd of 6,676 with just over 1,000 tickets given away.
The Brit had 47 stitches after his unanimous points win over Wallin and promoter Frank Warren revealed his fighter now faces a race against time to be fit to begin his next training camp on time.
"We won’t know for sure if such an horrific cut has healed properly for another six or seven weeks", he said.
"Tyson will not be able to do any physical exercise for two months. Then he will need to start sparring just before or just after Christmas to get in the seven or eight weeks he will need in camp to be ready by mid-February.
"Fortunately it was a clean cut, not jagged, so it didn't need to be reopened for plastic surgery.
"But we will still need to be sure it is OK. This is always the risk with boxing. One punch can change everything."
