[hcobb]

Here's my calculation on the production costs.

Weekly costs:
IQ 18 wizard $200 (ITL 59) + $50 (cost of living) = $250
6 Apprentices at $50 each = $300
Lab rental $150
Supplies $50
Total / week = $750

The IQ 18 wizard will be around DX 12 so it takes 5/74.07% or around seven weeks to produce one ring so total production cost is $5063

Applying a minimal markup for management, facilities and sales gives a sales price of at least $6000. Taking that as the rock bottom "Very friendly" result from ITL 166 gives a flat doubling of the listed magic item prices for common items. Weapon/Armor enchantment is easier and so doesn't need the doubling.