We have a huge site, with a huge list of fields where we are using Commerce for a tiny part.
Trying to decrease the memory usage, I noticed that the entity properties are loaded from the cache and use 3MB memory for that. I tracked it down to a single call in commerce_product_reference_entity_view(). We are not using product references at all here, so this will never do anything except loading all these properties on pretty much every request.
While there are places that use more memory, this one should be easy to fix by conditionally creating the wrapper if not already set inside the foreach.
Will try to come up with a patch later but wanted to write this down so that I'm not forgetting it.