That's my bread-and-butter. I take a good SaaS and strip it down so it's simpler for people to use (and for me to build). Then I sell it for significantly less than my competitor. Simple & cheap is "better" for some people.

The trick is to find a good niche, so you can build a bunch of semi-related SaaS apps and cross market them. I've found developer related SaaS (web browser testing, PDF generation, log analysis, cron notifications, etc) are highly saturated.

To be fair, none of my products qualify as "startups". But building a lifestyle business has a lot of perks (no stress).