I think it is true that packaging is important and that the package must be able to keep the treasure safe inside. However, the role of packaging is to keep something safe and the packaging doesn’t compare in value with what the treasure contains. I have a mobile phone here which I value and so I bought a good cover for it, in case I drop it. However, I would refuse to pay more for the cover than the phone itself.
Paul tells us in these few verses a number of things that are truly important when it comes to understanding our role and our importance in Gospel work! Put very succinctly, the treasure is “not us, but Christ.” We are light bearers but we are not Christ himself!