I'm wondering about not being able to buy the DLC just once, and the use it on all my platforms. Do I really have to buy the DLC for my iPad, the family iPad and the PC (Steam) each? Since a lot of us use several platforms, there should be an easy way to have the DLC on all of them, without buying it several times.

Is it a mistake, or a conscious decision?

It's likely just because they're completely separate platforms. FFG would have to have a sign-in system in place and hold account information, etc. That's a pretty expensive piece for them to build for this app. I don't disagree that it sucks, though; I'm somewhat in the same boat. I started out using my phone to play the game and then started using my laptop for the larger screen; it would've sucked if I had to mess with DLC at the time as well.

you talking about expense for FFG! I'm Pretty annoyed about the cost of the DLC. in Australia the are charging $7.99 for on mission on top go the $160 they charged for the base game.

Well... hobby board games (aka, not Snakes and Ladders) are a bit of a luxury item to begin with. It seems like Australia, in general, has inflated costs across the board though. I think that is more of a country thing than a company thing in this case. From what I understand, video games are very inflated as well there?