https://www.trueup.io/tech-stock-declines
Out of 17 YC companies that have gone public, 3-4 have been delisted, 7 have lost >80% of their value, another 7 has lost 10% to 50% of their value. Only Reddit and Instacart have gained 47% and 31% respectively. Sounds a lot like bagholding to me.
Here: https://www.marketsentiment.co/p/the-yc-report
Regarding Stripe, if investors own just 50% of the company (highly probable, given how much they've raised), it'd take 350 years to pay them off. Payments is a high-volume, low-margins business.
In fact, even if Stripe 10x'd their revenues, it'd still be 35 years before they bought out all their investors. if you think I'm being unfair, look at the numbers Paypal and Adyen are doing and assess their valuation and you'll realize Stripe is extremely overvalued.
Adyen is trading at 60x profits; PayPal is trading at 2.7x revenues and 19x profits.