Have that person go and buy the amount of fabric you tell them. It'll make a big difference in how much it costs, and might come as a big shock to them. There are so many sizes for quilts that a person who doesn't quilt might have a very low idea of what it really does cost.
Right off the top of my head there are lap robes of several sizes (my daughter is 5'4 and would take a smaller lap robe than her 6'5 hubby) and there are crib quilts, bunk beds, twin beds, standard beds, both regular and extra long and also extra wide, doubles also regular and extra long or extra wide, queens also with all that, kings, when we looked at them there were Eastern Kings, Western Kings, extra wide and extra long Kings, well, you get the message that each bed can be different. And my sister and her DH had a mattress specially made for an antique bed, so it's best to get some idea of what size you are committing to making.
Good luck on that and show us the finished product.
And would the pillow shams be for regular or queen or king pillows? I have a queen bed but insist on king pillows. And one of MY complaints is that they don't make the king pillow cases big enough, it's a real fight to get them on my pillows.