Damn bro, that is some crazy expensive stuff.

Let your friend buy what he wants. You can say, "whoa, that shit is expensive, you really want to buy that?" in a good way. Try to avoid saying, "you're getting ripped off man! That's stupid to buy it for that much"

He felt insulted somewhere down the line.

I'm sure he'll get over it and tell you you were right, because I agree, that much for that cost is D-U-M-B.