There's a non insignificant number of people who plead guilty to murder for that same reason (to avoid death penalty) but are later exonerated via DNA evidence.
How many of those cases involve defendants who can afford the lawyers that Backpage.com's execs can afford?
You can just say "significant".
You can also not not say not insignificant.
Off topic here. But, I see those phrases as different, as most people probably do. I see non insignificant as...a few. If they'd said 'significant', I'd assume a high percentage.