I do a lot of graphic design in Photoshop and this would be simple to automate with actions. What an action is in Photoshop is the ability to record you doing any process, this is how you automate things in Photoshop. It can be as simple as saving and closing a file or it can be really complex doing hundreds of things. That combined with smart objects would make this simple.
What do you wanna know? I can only speculate on someone's method. Can't tell you for sure.
In general if you are able to "templatize" any work and able to sell it you can bank hard.
The trick is to be able to sell templatized/bespoke work.
If buyer want custom work instead of bespoke work you gotta filter them out.
there must be some online paid website for this, otherwise it's impossible to do it manually, i have done providing billboards design service and there is no way to do it automatically via photoshop. there must be a website with thousands of infographic designs on which you can simply put your buyer log and it paste on every design and you can download all design in 1 click.