Artik 710 modules are available from DigiKey for $53. They have 1G of RAM and 4G of eMMC, but no SD slot. No ethernet connector on the module either (but you get Wifi and Zigbee radio).
Not having ethernet on the module is one strike against them. A second is that I have been unable to find a schematic for the module anywhere online (there are schematics for all the support boards). The development ecosystem is the third strke -- it seems to be at least partially cloud based, which I hate.
If you buy the starter kit, you get a Platform IO board with the ethernet connector (and Phy presumably). No SD card on the Platform IO board either, apparently you install software over the cloud. However the starter kit costs $201. It is not clear that the starter kit is truly necessary. It may be possible to install software via Wifi.
I was looking for linux images as "img" files to copy to an SD card, but apparently that is not at all how things are done. They are into a "cloud based" development system, and offer an Eclipse based IDE (for Linux as well as Windows) that implements this.
Tom's electronics pages / email@example.com