I run a saas that is profitable: https://PhantomJsCloud.com
It's a pretty simple concept: providing PhantomJs or Chrome Headless as a REST API.
The thing is, the SaaS itself is only about 1/3 the work. You need a website, account management, and billing too. Today, there are perhaps other services you could leverage that can help reduce this initial burden (Kong?) but a few years ago when I started my SaaS, nothing really met my needs. Hope it's easier for everyone now!