That time they could save is likely much more valuable than just the one time fee, and constant improvements and features for them could very well justify a nice recurring subscription fee.

http://www.thedigitaldesignco.com/graphic-design-subscriptio...

not exactly just logos but people seem to try and SaaSify everything.

But your two examples here seem exactly the kind of long-term customer relationships that benefits from SaaS. And may in fact be underutilized. These are high-touch, deep background kind of gigs, rather than impersonal service sites. I want to have an ongoing conversation about my task and I'm willing to pay a retainer++ for that privilege.

So there might be a substantial drop-off in revenue next month as there is no recurring revenue from existing customers.