It's handy for fixtures and smooth steel vise jaws.
Grainger ($212, 24" x 4" x 1" ± 0.001" thickness),
McMaster ($180, ±0.003") &
MSC ($256, ± 0.001") would be places to look for pricing guides): just because it's Starrett doesn't mean anyone would pay Starrett prices for some they can get elsewhere for half the cost.
I picked up some from eBay a few years ago because it was cheaper than plain CRS and it would save time machining the width & thickness for a particular project. I also picked up some from MSC since A) they had at at the local depot, B) price was similar to what I got off eBay and C) was the size I wanted.
For current comparison, the Seller I purchased from 3 years ago on eBay has 24x1x1/8 for $13.63 (free shipping) and MSC wants $26.17 (+ shipping). What I bought surplus on eBay had MSC stickers. However, MSC has 24x1x3/32 for $24.40 (fee shipping) on eBay, and wants $27.31 (+ shipping) on their website. Bottom line, you're looking at probably 1/4 — 1/3 of the lowest industrial source price you find online to sell it yourself.