why she felt she had to point out that mahogany exists and is expensive

Hunger Games is aimed at a fairly young audience who might not have encountered the word before? (I read a lot of fantasy as a kid, and only my mother's Handbook Of Tree Identification enabled me to know that that fancy magical wood/tree called "rowan" that cropped up sometimes was a real plant and not, y'know, just another fantasy element. I certainly didn't have any in my yard, after all, and I had plenty of familiarity with fantasty-novel type MacGuffins, so.)

Or Hunger Games is aimed at a fairly young audience who might know that "mahogany" is a furniture colour, but not that it's named for an actual tree, given how little furniture is made of actual wood these days (rather than plywood + veneer, the colour of which doesn't affect the price much). *shrugs*