Field notes
Compare the whole offer
A larger order can leave more money overall while leaving less for each hour you work. Start with a normal order or another realistic option, then enter the proposed offer. Compare the same kind of product or service and use the same approach to costs in both columns.
More money can mean much more work
Ten sales at $100 each, with a $60 cost per sale, leave $400. If the order takes ten hours, that is $40 per working hour. Twenty sales at $85 each leave $500 at the same cost, but twenty hours of work bring the hourly amount down to $25.
The proposed order leaves $100 more and takes ten more hours. That difference adds $10 for each extra hour. The larger total alone does not settle the decision.
Let costs change between the options
Bulk materials might cost less, while paid help or delivery might cost more. Put expenses that repeat per sale under Cost each. Put setup, delivery, or other whole-order expenses under Other order costs. Count each expense once. To compare an order with doing none, use zero quantity, zero order costs, and zero working hours for the other option.
Include the time behind the sale
Include preparation, customer messages, making or delivering the work, and administration in your hours. Keep your own pay out of the cost fields here; include wages paid to other people. The hourly amount is what remains for you and the business after entered costs. It is not take-home pay, and unentered expenses and taxes still need covering.
Try a less favorable version
Increase costs or hours and see whether the benefit holds up. These are two complete alternatives, not a forecast of extra customers. Consider available time and other work you would give up before accepting.