Interesting observation: Pantera-308 metal

I had what I thought was an interesting observation the other day. I kind of absent-mindedly rapped my knuckles on the fender of the Pantera and then did the same thing on the 308 and encountered two very different sounds. The Pantera sounded kind of thin and hollow while the 308 sounded thick and solid. I thought perhaps the front differed from the rear fender, so I tried it and again heard the same difference. On the Pantera I felt like I was hitting sheet metal while the 308 felt like solid metal. It reminded me of the sound difference between sheetrock and a wood support when you rap on a wall to hang a picture. I have always attributed the price differences to mechanicals, engine, the name, etc but is there that much of a difference in the metal used between manufacturers or is there some other reason?