even if you used scraps- guess-timate the amount of fabric in your item (top, backing, batting) and price it at the average for yardage in your area; determine how long it took you to make the item & decide how much per hour your time is worth... add in the cost of quilting (if you were to pay someone to quilt for you) then decide what your (market) will allow/handle.
ie: table runner 18" x 42" = 1/2 yard of fabric (2/3 to have some fudge room- for backing) then the top is pieced-so 1 yd for that- at $10 a yard = $16 (about) + a craft batt at $7= $23 - took 2 hours to make- minimum wage is ? $7.75 *a guess* = $15.50-----$23 + $15.50 = $38.50...could you get $40- $45 for your runner?? i just sold one for $45. but not at a craft fair- sometimes those get decent prices- sometimes people expect you to give yourself away...have to find out what the market will support.
and you need to figure out your own (formula) that works for you and your items.