Honestly more information would be needed to correctly judge the value
1-what kind of stock is installed?, a magpul prs stock would be more than a utg 6 position collapsable stock
2-what kind of internal parts? A hyperfire eclipse trigger would be worth more than a milspec trigger (in fact a hyper fire trigger would probably be worth more that the assembled lower)
3-factory built or franken build? (I.e. do you have the factory shipping box for the assembled lower vs a box for a stripped lower?)