Would a $50 IEM be 90% there?

No. Not even close.

There are different styles, like open back vs closed back. Different tunings. Different materials. Etc.

Do you need to spend 1000’s more? No. But you have a very V shaped tuned IEM that doesn’t have much in the way of technicalities. Other headphones will be tuned differently and will sound different.

A Sennheiser HE-1 which is considered the “worlds best headphone”, is going to be miles better. (It’s $50,000 though). You don’t need that though.

You’ll notice significant differences with something as simple as an open back. You can get into one of those for less than $100.

Ultimately you have a starting point. But yes, it does improve from there.