Got my bf concert tickets but im scared he’ll buy them too

I (20F) got my bf (23M) tickets to see his favorite artist for Christmas.. he mentioned the concert to me a few times after I already bought them, saying that the tickets weren’t that expensive. I even saw him on Ticketmaster scrolling through the seating.

I tried to steer him away from buying them, saying that he should focus on his bills first and then see where he’s at with money before buying tickets, distracting him with other stuff, etc… but I’m terrified he will buy them anyways. I even got his sister in on it to have her make sure he doesn’t buy them when I’m not there to tell him not to.

I’m sure he’s suspicious already, but im trying not to tell him until I show him the tickets on Christmas.

What are some other ways I could get him to not want to buy the tickets without telling him I already bought them??? Any advice helps it’s only a few more weeks.