It's a little vague to say "more stuff". Perhaps you can elaborate?
Is it more quantitatively, as in 1GB of space, more if you pay (eg. the paid value is the same type as the free value, just more). Or is it qualitatively a different thing, as in more features that more useful (eg. the paid stuff is qualitatively different than the free stuff).
If it's the quantitative scenario, the amount of stuff desired by customers that pushes them over the threshold to paid can be balanced against the minimal amount of free stuff that is still useful. I converted to Evernote paid after a few years because of a storage limit. I was invested in it enough (and the switching costs high enough) that it was worth it. But it took me two years to convert. And many users just never do because they use it differently than I do.
There is probably a profile of your users that will convert. Find out who they are and get more of them.
If it's the qualitative scenario, the paid version is solving a different problem for the customer than the free version, and one that is painful enough to pay for. I used Buffer for business for a while because I need to manage many accounts and the reports were important. When I left that job, I reverted back to free to run my own stuff.
If you have a different feature set for free, make sure some part of it leverages network effects. You're paying those users essentially, so it's part of your Cost of Acquisition for the paid users. Make sure you consider that in your numbers.
There is no shortcut to simply finding out what your users really value, and testing different conversion mechanisms to convert them.
- Are you using drip email campaigns?
- Do you have explainer videos?
- Do you offer free upgrades with a time limit?
- Do the free users have a real reason to convert? What is the "Job to be done" of the paid version, how are they solving it now, and how is yours better than that?