On my two recent expansions, I hit both two Medium Mossrocks in the same expansion (at $350k each) and then my next expansion had the large Mossrock at $1.5M.
I don't have over 2 million sitting around, it will take a while to save that up. Did I just choose the wrong two areas to expand?
Shouldn't there be a balance in the number of coins/maps needed vs. the coins needed to clear obstacles?