The first dollar is metaphorical. Substitute first sale/income if that makes it easier for you to think about. (As an aside, I've seen many businesses frame and display a single dollar representing their first sale. http://framebiz.com/index.php?products_id=187)
Yes, I understand that it should be metaphorical but in this case it's quite literal. This story demonstrates more of a user acquisition exercise and dresses it up as a SaaS business exercise. You will have different problems charging $1 once versus $10 per month. This story is really not about SaaS products.
I really think you're missing the point of the article and why people appreciate it. It's extremely straightforward: "Hey everyone, here are some interesting stats + an entertaining story about what went into making the first sale at a SaaS business." It's not pretending to be anything more than that.
