It's not a sin I believe those who do have alot of stuff should thank the Lord for it. Not many people around the world are that fortunate and have very few things. Always appreciate what you have, unfortunately many people take their blessings for granted. However we should not put anything of this world above God. Everything in this world will pass away but Gods word & his promises to his people will never pass away. The Lord also mentioned treasure in heaven for his people that will last forever.