Finally my experience with the portal was:
I did the first 3 missions (normal, hard and insane) and got 45 tokens and more than 100,000 coins.
From there I did 10 or 15 more missions in insane mode and each of them gave me 9,650 coins, except 2 that gave me a little more than 28,000 coins.
Conclusion: BB insane mode gives more coins. And … it seems to me that there was a bug or something that was not right.