Howdy! Apologies for all the confusion, hopefully I can help clear things up. To start, a lot of what I'm about to say can be seen discussed in our blog post about the Demiplane & Roll20 Integration Update, I highly recommend giving it a read!
1. There isn’t a Spider-Verse Expansion Compendium on Roll20. Instead, we offer a VTT Companion, which includes two Art Packs and an Add-On featuring Dynamically Lit maps and tokens. With that Add On, you'll get access to all of the new characters in your library to use with drag & drop, alongside your other Roll20 Sheets. The Avengers Expansion will also be supported by a VTT Companion only on Roll20.
2. The Marvel Multiverse Role-Playing Game Spiderverse Expansion is available on Demiplane. You can see their post here discussing the expansion! It's a rad one, for sure. And, if you buy it over there, you get the VTT Companion mentioned above for free. In addition to that, Marvel The Multiverse Role-Playing Game is participating in our Cross-Platform Sync, which is a feature that allows you to purchase a game
title once and access it across both Roll20 VTT and Demiplane platforms. If you link your Roll20 account to Demiplane, you'll immediately be able to experiment with Demiplane's experience for the Marvel sheet, in addition to Pro subscribers automatically unlocking the same perks as Demiplane subscribers. Which is great, because...
3. Our Demiplane and Roll20 integration is ongoing! Looking ahead, we’re working on integrating Demiplane’s Marvel Character Sheets into the Roll20 VTT this summer (Apr-June). This means you’ll be able to use all your Demiplane Compendium content directly within Roll20! Pretty soon you'll be able to take a look at both sheets (Roll20 and Demiplane) and choose whichever you'd prefer for your games. If access to the Expansion content is high on your list of interests, then I definitely recommend checking out the Demiplane sheets! (They're also just really, really rad!)
TL;DR: No $150 purchase required! Cross platform sync unlocks the whole thing on Demiplane, and if you end up grabbing the expansion over there, the VTT Companion comes with it as a bonus!
Let me know if you have any other questions! I'd be happy to answer them.