Last time I looked (which was a while ago), I needed 2 Grrrilla cards to upgrade (I was at 2/4), and I could get the missing cards with a whole bunch of gold. I chose not to because I didn’t have the coin to upgrade.
Just now, I managed o earn the Grrrilla card reward in the event. I went back to upgrades to see what the new gold price would be for the last card out of curiosity (still no coin) but I’m no longer given the option to do so. Did the last update remove the gold upgrade option completely?