I could see a lot of small groups adopting this -- college extracurricular groups, a team at a church, friends organizing a short film -- and if you're focusing on usage metrics, that whole universe could prove to be far larger than the business market, at least before it's included in G Suite. Think of how many people use Forms+Sheets for that stuff right now.
However, my $0.02 would be that, right now, if I were one of those, I'd look at the landing page and assume that I'd quickly run into a limit and be tricked into paying $10/user/mo., so I'd avoid even trying it out. The 1,000-row limit seems like something I might easily run into, for example if I were simply importing all the alums from the organization's 30-year history.
I wonder if you couldn't come up with a better separation between free and paid that didn't depend on storage, but solely on features? For example, imagine if Sheets were free but charged if you wanted to use pivot tables and database connectors -- something like that. (Also, total storage is hard to estimate in advance, perhaps better to have a limit on attachments per-row? E.g. 64 KB, and it will automatically convert images to JPEG with lower quality/resolution as necessary? Otherwise everything is stored as a link to someone's Drive file?)
I just think if you communicated this as "100% free" but then with a "paid business integration add-on" or something, people would be a lot more willing to try it out. Again, best of luck!
