All of the plans that are available through the PWS Marketplace are listed. If that is the largest plan you see, then it is the largest that our partners offer through the marketplace. Pivotal does not directly control what plans are available through the Marketplace, it's up to our partners who actually provide the services.
You have a couple options:
1. You can reach out out to the support team for our partner, ClearDb in this case, and ask them if there are more plans available of if they could enable more plans.
2. You can create a plan outside of the Marketplace. You are not limited to using what is in the Marketplace. The Marketplace is really just convenience. See this KB for details.
https://community.pivotal.io/s/article/Are-you-restricted-to-use-the-only-service-providers-that-are-listed-in-the-marketplace
Hope that helps!