Ok let's use your math.

So assume they only get 30K visitors/mo. At a 7% conversion rate (which is listed in the article), if you assume that each clean is on average $50.

That's a cool 30,000 * .07 * $50 = $105,000 in revenue from NEW customers every month. - i.e. $1.2M in new revenue per year.

If you also assume that what they have been doing in the article is true (i.e. working on keeping customers happy) then they likely have repeat business (given that people always want to keep their place clean), it's definitely possible that with a $1.2M revenue growth yet per year - based on current traffic trends - that they could be doing $4M/year.