I’ve never seen an ad for Moxie, but Wikipedia says it’s still made.
At one plant in Georgia or somewhere, and sold mostly in Maine, mostly during the Moxie festival.
There are probably dozens of specialty sodas that have little or no advertising, but sell well enough by being pushed to stores by wholesalers. Mello Yellow is one that was popular in my area when I was a kid, and I think it’s still made on about the same terms as Moxie.
Mello Yello is pretty widely available in the South. It’s manufactured by Coca-Cola.
First of all, I prefer the size of their packaging’as it is far easier to scale up than down. For example, the brownie mix makes six brownies (a loaf pan) and that’s the right number of brownies in my house.
However, it is not a matter of smaller packages – Jiffy products are about 20%-60% cheaper on a per-ounce basis than competing products. I compared them head to head at an online grocer… guess what?
Jiffy: 8 oz biscuit mix – $1.59
Bisquick: 7.5 oz biscuit mix – $2.19
the Jiffy package is actually larger, and still about 25% cheaper. Where’s your fancy math now, eh? 
Disclaimer: I don’t work for Chealsea Milling, I just have an inordinate interest in their operation.