WIBTA if I didn't buy matching clothes for my friend's wedding where I am best man?

So one of my best friends is marrying next year, and he asked me and another friend of ours to be his best men. I said I would be honoured. But now he is telling us that his fiancé wants us to have matching clothes for their wedding.

It just so happens that I recently bought some really fancy clothes for my cousins wedding and I deliberately picked them because they wouldn't ''go out of fashion'' so I could wear them to other occasions as well. I'm not a person that would wear these kinds of clothes regularly.

I don't really feel like buying another set of clothes for this occasion because I spent a lot of money on the last ones and I would likely never wear these new ones again because they have to be a specific colour.

WIBTA if I didn't buy these clothes?