They are pretty big, so figure $500 for oak lumber and maybe $100 for other
supplies.
Making them cabinet quality could easily take 2 weeks, at $60/hour; that is
$4,800.
So, yeah, we are in the $6,000 range easily enough.

Now, if you just want some painted pine bookcases, and want them to look
"nice", you could probably find someone to make pretty decent ones for under
$2,000.