CMT means lower profit margin for tailor so most tailors in Singapore, especially those without a workshop, will not do it or charge the same prices. They accept regular customers for CMT out of goodwill because the pattern and measurements were already done and if customer is pleasant to work with, they don’t mind CMT work since it’s basically cloning the previous pattern and save time on fabric consultation and taking measurements. Otherwise, there isn’t a fixed price for CMT and it can vary according to the fabric that you bring to them. Even bespoke tailors like TCR and sonofagan offer CMT but their CMT price compensates them for their skill level.
And rightly pointed out, it is finding a CMT tailor whom you TRUST is the issue, as cutter and maker have to get it right the first time as there isn’t a replacement fabric that they can order, since they have to work with your fabric. Also, “a tailor” can be multiple professionals who ought to be paid for their services. The measurer is normally the designer who provides the fitting service and design consultations, and some are cutters who draft and cut the fabric. Then, the cut pieces are sent to the makers, people who sew the pieces together using the machines and finishers who finish the suit by sewing the buttons by hand, etc. Add up all the labor charges, the CMT price will not be low in Singapore.