Standard margins depend on your industry. Find this out before you go further. If you don't know, call some other catalog vendors of similar products and see what they're doing.
Do you have somebody in your industry you can ask? Somebody with specific experience in this product area? If not, do a web search, and find somebody.
Tim Berry is the chairman of Eugene, Ore.-Palo Alto Software, which produces business-planning software. He founded Bplans.com and wrote The Plan-As-You-Go Business Plan, published by Entrepreneur Press. Berry is also a co-founder of HavePresence.com, a leader in a local angel-investment group and a judge of international business-plan competitions.