I dunno... This may not be for everyone but if I consider the amount of time spent correcting diagrams in excalidraw $10 / month seems more than reasonable to me: as long as it's for the creator not the viewer.

Thanks. I haven't yet got to looking into Confluence. I used to use a Confluence plugin for Lucid charts and I guess something like that for Line9 would be useful if it gets much traction. I don't know whether the embedding options in the Pro account would display well in Confluence.

On pricing, I'm testing numbers at the moment so your feedback is valuable. Anyway, please do paste in your bad layouts - I'd love to hear what happens.