[vanisleflamesfan]

The two big things IIRC are the quality of the grain of the leather on the 'seating surfaces' and whether or not the other surfaces of the chair are of the same grain. For example, some of the less expensive chairs will use a poorer quality leather on the sides and back. This won't make much difference if the leather is dyed a dark colour, but often if the chair is light or a natural grain colour, the differences in leather quality will be visually evident.

Obviously, the most important thing is the quality of the grain on the seating surfaces, as this is the leather that is going to get the most wear. If you want to save money, get the best quality on these surfaces and less quality on the sides and back.

I hope that makes sense.