check out feinternational.com (OP mentioned them as well). I've been subscribed to their "Buyers list" for over a year and I've seen many nice saas businesses listed.
It's the last quarter's numbers annualized to a year so if there's been a spike in the last quarter that isn't seen in prior financials that's a point for negotiating the price. And it's also based on discretionary income so that "profit" is not necessarily the actual profit the business took in. A lot of expenses are considered discretionary but probably have a positive ROI.
So while 3-4x is normal (really 3-5x depending on the industry) the numbers on FEI tend to be a tad high but not unreasonably so.