I was under the impression that vendor machines sell stuff at 100% base price regardless of the market conditions, so cramming them into a vending machine when there's a price hike is not a good idea?
I caused a market crash on those vending machines because I had a few requests for metallic items...
Even in high market situations, things can be purchased at below base price, so you can still profit. And, well, does it look like he needs the cash?