The difference in multiples paid in private buy-out deals mirrors the data that show differences in required rates of return between large cap and small cap publicly-traded securities. Both emphasize the risk-return relationship and the phenomenon of smaller financial size relating to higher investment risk.
Once EBITDA levels are broken out by buyout size, the difference becomes all the more transparent: The median multiple for sub-$25 million buyouts, which includes many add-ons, is less than half (5.6x) of the median valuation commanded for $2.5 billion+ buyouts (12.3x) over the same time-span.
https://pitchbook.com/news/articles/why-deal-size-is-critical-when-analyzing-pe-buyout-multiples
