I came across this site and I think it would be really helpful to get a general idea of what things cost at home before you begin your bargaining.
This stuff looks to be pretty high quality with prices listed in USD, so of course you would expect to get it much cheaper in Egypt.
But check it out. Tomorrow is my shop til I drop day in Aswan, and I've found it very helpful to find out about alabaster etc. since I have no idea it's worth.