For me it’s not unfair. It’s not however worth spending food or gems or go out of the way in any kind to achieve the maximum amount of postcards.
The best equipment could replace my lowest camp item from 120 to 158, (China) so not too bad. However, there are other ways to get such equipment and so I bought green rings instead for a start. I think I will still get one of those (150 postcards, would give 18 green rings) but I doubt that it’s worth the effort to try for both.
So actually it’s not a „OMG, I HAVE to have this“ situation for me, but still better than for endgamers that don’t waste a thought on that equipment but take the rings. It all depends on the strenght that your camp has already. At the beginning of a region, it’s nice.
I go for the 10x XP and THAT is very worth it for me.