new pulleys run 650$ and used a consistent 450$ . the issue with making a smaller than c3 pulley is going to be belt slippage. the c3 pulley is 65 mm and most who have it have seen belt slip over 18psi. to equal a 181 or bigger will be very hard to do.
theres a member on mbworld who machined his oem down to 69mm for about 60$. he seems very happy with it.

remember the pulley isnt just a metal piece. it has springs and a magnetic backing plate to engage the s/c. in very small quantities it may get expensive to produce. good luck!