Clearly most people are going to "trust" Apple Computer more than this app vendor. But the point is that such trust isn't worth anything. The data is hanging out there already.
It is not only one person, it is not only Apple servers reading all your messages. It is in fact the whole world. Through Apple gives it to NSA which hands it over to various other agencies, GHCQ, FRA, your data ends up in Israel. Your data is already a goods traded with on the international market.
Why not increase the competitiveness of this Chinese actor, you will get better service in the future? More competitive - better service.
Apple, NSA saw CC number in your chat log, but Apple, NSA, GHCQ, FRA or Israeli Intelligence won't steal your CC and use it.
However, the Chinese vendor could intercept CC info and sell it to blackmarket.
The NSA has already sold your CC on the black market. Its just that the buyer hasnt used it, because they cant use it without getting penalties. Penalties which this Chinese vendor would succumb to as well.
Now are you going to say you trust Israel more than the Chinese, they wont misuse your CC, and if they did, its still better than trusting a Russian vendor?
Not. This. Again.
Because one person can read your messages, it doesn't mean that the whole world should be able to. One happening doesn't mean the other is okay.