My point is that companies that are slow-growing are rarely sold, and when they are, they usually aren't sold for much. The eye-popping valuations for companies like Whatsapp, Instagram, and YouTube were all based on growth, and on strategic fit with the acquirer. When an acquirer wants you for these reasons, there are large time pressures and asymmetries of information you can leverage to extract a lot more money than the financials would dictate. (Whatsapp, for example, sold for something like 1000x revenues.)
Small slow-growing companies almost always sell based on financials, and typically for lower multiples than an equivalent large public company would (because their revenue is more concentrated in a few customers and so they're more exposed to revenue risk). I've heard 2.5x revenues or 15x profits as numbers commonly batted around; above this and there's virtually no reason to buy the company vs. invest in public stocks or apartment buildings. On a typical 10-person company that makes a profit of about $300K on revenues of about $2M, this comes out to a sale price of roughly $5M by both valuation measures. Own 1% equity (this is generous, and would usually indicate employee #1 or 2) of a $5M acquisition and you get $50K, which is probably a lot less than the salary you forego over a few years by not joining a big company.