"Your 30% may be much more profitable than someone in residential service trying to recover the time of a low-cost special-order item"
Yes it is, usually more profitable, that 30% on a job with low burden, can usually cover the burden cost and allow for a small profit.
Mark-up should also include, a burden amount, on the material, to account for Guarantees, and warranties on material, and the recovery costs of any labor needed to provide these services, some states require you to warrant your work for 1 or 2 years.
[This message has been edited by LK (edited 10-01-2006).]