Having lots of money isn't materialism. Neither is making lots of it or spending it on expensive goods or enjoying the process of shopping.
Since love is a commitment to something at the expense of self, surely it's the same with the love of money and material goods.
How do we know what we pursue isn't vapour? That what occupies us day after day is not frivolous but a worthy pursuit that will bear fruits that remain?
So where the sense of guilt come from when we spend on an unusually expensive item or series of items? Perhaps it's the innate prudence that cries for self-control in the face of future needs and worries.
Well, we know we shouldn't be defined by things--not to let them have us. Yet sometimes we don't even realise we've been had. By our things, that is.
If you were to lose everything you have--absolutely everything--would you still be you?