It is supply and demand. Pastels are co-domnant and have been around longer and bred more so more are availible. Prices will still vary from quality of morph. Albinos are the oldest morph but since they are recessive, they are harder to produce and supply is slower. Thats why your recessives keep their prices better.
I don't know about albinos keeping their prices better. When i started looking around for mine they were $1800 now you see them going for $700 to 650.