Earlier quoted context omitted.
We're working on a business version of the product, which will be a monthly fee on a per user basis. We're unsure of the exact pricing yet. It definitely isn't slow for all users! However, there are some that send so many emails that any incremental speed-up is very helpful. Plus, we're looking to start working on mobile, where it should be most useful!
I think it's more than incremental speed up - it's the amount of mindspace it takes.
If that's the case, that's a fascinating insight - thank you so much for sharing it!