The site is also a bit deceiving calling this a 4 hour top. I think it would take me longer to make that top in 4 hours. Then add to it the time it takes to prep fabric (I am a prewasher) then get the quilt loaded on the rack and quilt it.
Additionally I would NOT make a special trip to the fabric store for the fabric. I would order on line. But if you are concerned about matching exactly you need to figure for your time to get to the LQS, time spent at the LQS picking the fabs and getting them cut and checking out then travel time home.
Also no telling how spendy matching fabrics will be. 5 1/2 yards for the top. Conservatively estimated at $10 per yard. Then, because I wouldn't want to spend time piecing the backing I would want a wide back so figure 2 yards of 108" wide back fabric at around $16 per yard (usually buy this on line, may be more spendy at an LQS) you are talking over $90 just for fabric (assuming 6% sales tax). Then you need a batting. another $20 (conservatively) $10 for thread used
So JUST your raw materials are conservatively estimated at $120.00.
If this quilt top takes only 4 hours to make (personally I think it will take longer), figure another 4 hours travel and in the shop time for fabric, approximately 4 hours for fabric prep (washing ironing applying sizing if you use it and folding for cutting) and another 6 hours to load it on your rack and quilt it. I don't know how you bind but I bind by hand so that would take me at least another 4 to 5 hours. At minimum wage $7.40 per hour plus self employment taxes (safest to add 50% on to the minimum wage) you are looking at another $255 for labor. So the absolute LEAST I would charge for making this quilt is $455 but I don't work for minimum wage so Holice isn't too far off on that $650. starting point.