This exact scenario played out in Israel. A coffee chain that advertised coffee for 5 NIS (about $1.20) showed up from out of nowhere and completely took over.
And likely they're either:
1. Dumping into the market to gain market share and decimate competition which is often illegal, depending on your locale in which case that coffee will be a bunch when they own the market (or they go out of business)
2. They have suppliers that are so tainted nobody buys their source and you probably shouldn't either
There are so many coffee shops in Israel, so I doubt they can take over the market. There’s a few major chains, but even Starbucks tried to enter that market and failed miserably.