First time we went we didn't go in - it didn't look much and it was around $15.00 admission.
Next trip we were walking through and saw that it was free so we went in - I enjoyed it.
I am not an Elvis fan so the sequin suits and cars did nothing for me. But the hand-written lyrics to the songs, the report from his primary school teacher, his passport, his revolver, letters from his peers, ticket stubs - I can look at that stuff all day long. If you get a chance to see it I recommend that you go. It is better than it looks!
Edited to add - the gold and platinum discs are worth the trip - really cool to see them.