Valuation also depends heavily on components of a particular business, so it's not useful to just use one range. Does the business require the owner to run, or is a management team in place? Does it generate its revenue from 1,000 paying customers or 25? What is churn like? How fast is it growing? And bigger companies tend to have less risk in general than very small companies. FEI guides to a range of 7x - 10x for SaaS > $2m valuation (yes, this is somewhat recursive). The high end of that range is about a third the multiple Microsoft gets, but then again these are small businesses without Microsoft's competitive moats.
FE International[1] and Acquire.com[2] routinely publish excellent valuation guides for SaaS companies. I highly recommend to anyone looking to build or buy a SaaS.
1 - https://feinternational.com/blog/saas-metrics-value-saas-bus...
2 - https://blog.acquire.com/acquire-biannual-acquisition-multip...