I had this question just the other day on Facebook. Someone messaged me and asked how long it took and how much I charged. I proceeded to tell them about a queen-sized quilt I am working on as a wedding gift and that the supplies alone cost me roughly $250. I then proceeded to tell them that constructing the quilt would be an additional $250-300. They wanted a baby quilt by sometime in January. I told them if they purchased the supplies, the cost for constructing the quilt would be roughly $100. I then went on to explain the cost of the yard goods (at $8-10/yard), etc. and how much materials would cost them. I got a thank you and have not heard back from them since.
I thought my prices were reasonable, and everyone here is correct. Non-sewers do not have any idea what it takes to construct a quilt. They just know what they "think" they should be paying based on the quilts they see in the big box stores that are made overseas.
These days, I am happy to be able to just do this for myself and for gifts for others at my leisure. With a full-time job already, I do not need the added pressure of paying customers. I put enough pressure on myself as it is!