What are the specific components that are physically inside a interface or sole a/d converter that makes a cheap one like a scarlet solo sound "less detailed" (didn't want to use the word better) than an expensive one like a lavry gold??

 

all of the components matter, but the amps is where you will notice the most difference.
like any product though, sometimes you can pay for a name.

 

The difference expensive A/D converters make in recording or listening is tiny. If you can afford decent middle of the road ones, simply go with that and don't let it be a headache.

It's a headache and a consideration if you're trying to build a mastering studio, since in that case you definitely care even though the difference is tiny.

 

In Lavrys case it might be the whitepapers that prove anything over 42khz you cannot hear :DD