He shouldn't use Trezor even if it was for free, let alone making an investment, Trezor is using zkSNACKs aka Wasabi Wallet, a service that censorship transactions based on a dozen of reasons only to "protect themselves" from the law and biased governments, mind you that Trezor did not have to use Wasabi as there are a dozen of other alternatives, in fact, they did not need to implement CoinJoin in the first place, but seems like an excuse to please the authorities while pretending to be offering "privacy and anonymity" to its users. 

I know many people think Trezor is a great wallet with open-source code that is approved by the community and all that shit, to me, they are hurting the fungibility of Bitcoin and I would never use or support them.