So... wait... as someone who's already put the full $25 into the mobile app, and purchased various bundles and chests, I'm going to have to buy the full price Steam app as well now?
"Have to"? no. It's you that decides whether you want it on multiple platforms. If you do, you will have to pay. I do have some sympathy with your situation however, assuming that you paid real money for core game components on the mobile platform. But it's still up to you whether you consider it worth the money to purchase it on Steam. I didn't think it was worth the money on mobile, so all my purchases have been with Gold, I won't be buying it on Steam because (1) Quest Mode is going away, (2) I play it on my PC via an Android emulator and (3) I've spent quite enough of my resources supporting the extended beta/bug-bash that has been the mobile release, I have no intention of spending my money as well.