I'll give you an example of a signing that I was aware of that was proposed for a well known Australian Sports Person.
They were asked to be available for 3 hours to film some clips of them demonstrating their skills and to sign approximately 300 cards.
This person was making $8 million per year with salary and endorsements.
The response was they would rather than spend 3 hours on their day off at home with their family than earning less than $5K to do this work. If it were $20K for 3 hours work..... sure they would do it, but for less than $5K? Not worth their time given they are on the road a lot.
One Australian Sports Person (a well known Cricketer) who I was already a huge fan of and I am now even a bigger fan of, did a signing and asked for his signing fee to be split between 2 past legends of the game to help them out. They hadn't earned anywhere near what he had playing the game so it was his way of giving back to the game.
One company I worked at had a very well known Swimming Olympic Gold Medalist turn up for the day to meet with staff take photos etc.
He got paid $10K for a few hours work.
Another company I know of had a well known Australian Country Musician play for them for an hour - he got paid close to $40K.
With signing cards etc, manufacturers work closely with the managers of these players and most get a similar fee..... younger players less, stars more.
It's likely (i'm guessing here) that TLA said to BS, we will pay you a flat fee for signing and appearing on the cards (he is not on the NRL books anymore as a contracted player) so the cost of him signing/appearing was probably less than getting 16 Young Guns players signing.
Easier in terms of logistics too.... 1 player signing versus setting up signings for 16, especially with COVID in play.
Other players also have a very high regard of their standing in the game and charge huge amounts to sign...... keeping their auto valuable and also meaning that they wont have to sign often..... and if they do sign they get paid handsomely.....see Glory NRL and one specific signer there.
Cheers
Matt