A senior at FAANG is worth sometimes well north of 500K/yr. There are plenty of folks strewn about small software companies that do similar work to a senior or even staff/principal at a faang at wildly huge discounts.

It's hard to find numbers for the value of small software businesses (OP's quote), but this article [1] puts the number at $667k. If that's true, the engineer is SUBSTANTIALLY more expensive than the business (you're not just renting the business for a year).

[1] In the period between 2013 and 2016, the average sale was $667,000. While some sales were obviously much higher, and some were actually a bit lower, this must be an encouraging figure for a business owner to see.