There have been at least four in the last five years (https://docs.google.com/spreadsheets/d/1QT-vg7OHHhO9VvSHpgo7...).

There are many more notable bootstrapped exits, e.g. Mojang/Minecraft.

Lots of bootstrapped companies that could IPO, e.g. Mailchimp

And many other examples of companies that took very little money making their founders richer than comparable funded founders. E.g. Each of the founders of Wayfair made more than EVERYONE involved in the sale of Zappos.