It is true that you yourself won't have to buy the expansion to be able to trade the newly added Pokemon but someone will have to. So even if you could get away with just trading for them, someone will have had to buy the expansion so, to get them to be able to trade at all, money will still have to be exchanged for them.@Spirit from the sounds of it, you don't have to have purchased the expansion in order to transfer the pokemon being added, so I guess indirectly they're not charging for that, but Pokemon Bank or Home or whatever costs money I'm sure. I haven't really been following it because its like A MAGICAL PHONE APP that isn't going to be compatible with my phone so I don't care.
Plus, I wonder how well trading with someone who didn't buy the DLC would go because the person without the DLC will have nothing that the other person doesn't already have... So i wonder what the point would be.
So yeah, you can get them without paying, but someone somewhere still has to, so still not going to wholly excuse it.