Basic quality is pretty easy to determine. Look for good shape (in slipcast ceramics) and for the glaze, look for an even covering and even sheen with no bumps, on the glaze. Cheap ceramic plates will have glaze that it not even -- you will see a "wave" in it if you hold the plate at an angle. Put the plate down on a known very -flat surface. Cheap plates may have warped bottoms, or you may get 1 plate with a warp for every 3 plates that is flat.
There are some name brands that are known for high-quality at low cost. But if you hunt around you can find high quality at low cost, in no-name ceramics.
The standards for handmade ceramics are, of course, different than for mass-produced slip-cast ceramics. You do not expect perfect roundness in handmade ceramics, althouth perfect flatness would be expected -- no wobbles when you put it on the table.