If you don't know the coin but you can see that its blockchain is connected to a blockchain that you know and trust, you can look at DEX chain-to-chain trade vo

If you don't know the coin but you can see that its blockchain is connected to a blockchain that you know and trust, you can look at DEX chain-to-chain trade volume between your blockchain and the unfamiliar blockchain to determine its value and the amount of volume trustlessly (the volume would be measured in your own trusted coin coming from its own blockchain in a cryptographically verifiable way). If you can see that $1 million worth of your own coin is being exchanged for that other unknown coin each day and people are paying $50K worth of your own coin every day to cover cross-chain transaction fees, surely you can take a risk and accept that unknown coin as payment for a $100 product. The risk of the coin being a scam goes down with the amount of verifiable trade volume.