I was not talking about my own team in particular. I do have an extra trainees, because I picked up a cheap one in the off season.
But let me give an example for someone training guards (2 positions). (could have been me except I have too many players on my roster).
I believe that the optimal roster would be:
2 C
2 PF
2 SF
6 PG/SG
So there would be 6 trainees, that will get 48 minutes in League and Cup games. Your other playes would all on average 72 minutes. But with B3 they would get 96 minutes on average, which is too much to keep GS optimal.
So anyone in B3 really needs a bigger roster. So they need at least 1 PF to cover C and PF (resulting in 76,8 minutes on average on these position which is fine).
They also need 2 additional trainees, 1 SF and 1 Guard. The SF is needed to get average minutes lower than 96.
So when playing B3 you actually need to have a 15 man roster, for optimal performance. You might decide to go with less players but the performance will take a hit, as GS will drop.
So you will have 3 players on your roster that you do not need, and therefore have to sell or pay salary.
If you sell you will have to pay the agent fee - lets say 10-15% of (3*8000000) which is 240000 til 360000.
With an additional penalty on future sales as well. Or you could keep an have 14 weeks wages (14*10000*3) 420000.
So I believe that these cost are quite significant. And a lot of teams will not even be close to getting this sort of revenue from their B3 games. (I got about 70000 or something like that)
And yes I could keep my drafted players, and then the agent fee would only be 2-3 %, but since I do not really expect a draftee, that is even close to being good enought for the team if I get last pick. And most teams who make it to B3 will have last pick. And even if there is one decent player, you will not get 2 or 3, that is needed to get your roster to 15.
Yes, you'd have to blow some games in your main competition (or perhaps get temporary bacups for your PG and SF), but you could make up for it after you'd be out of B3.
In a tough division losing games could easily cost the Championship, as homecourt advantage is very important in the playoffs. And I believe winning the championship is the most important moneymaker.
Don't get me wrong - I really like B3, but I do not think it is a huge financial for most of the teams in it.