Not sure if this is already a thing since I know very little about flames but;
There should be flames with set properties which can't be customised in any way available to buy for a variety of prices. The purchase of these would be similar to 3D hairstyles where the detail and general awesomeness of the flame would determine its price. Maybe flame colour could be buyable although this would sort of defeat the point of the flames being cheaper than more customisable ones.

If this sort of thing already exists please tell me so I am able to close this thread in a futile attempt to hide my ignorance from the world.

Tell me if I need to explain anything in more detail.

It's not a thing, it dosen't exist. U can buy flames that are already forged in the past by others or u can forge your own flame.
Why would you want a standard model for flames when there are so many models to choose from. There are almost 4000 flames and almost every one is different.

It would cost less. But everyone would know it was a cheaper version. Don't you have to but the flame item as well as the flame texture itself ? This would replace the flame item. Custom flames would still be allowed .