The fact that even Amazon has switched to Stripe shows this.
And that is not even getting into the PCI, PCI DSS, SOC, I and II, etc compliance soup of self hosting.
Basically, here are the worst of the worst of Amazon's transactions, please take this risk onto Stripe's platform, then we will cut cost with full knowledge of exactly how much we will save by spending developer resources to cut out Stripe for this particular card type in this particular country.
I would not call this a healthy relationship, but rather stripe taking the marginal additional volume that Amazon brings to their platform to net slightly more money and get slightly more data points on weird payment methods.
If anything, the mind fallacy isn't the GP but on the commenters pretending that they love losing money. If we could pay $0 and get everything we want, we would. Everything else is just performative commenting to save face.
Also, this is kind of their thesis, isn't it? That developers want open-source software to do their billing, which they can modify themselves if they need certain features instead of relying on a proprietary provider like Stripe. Doesn't sound too outlandish to me.