One big thing about selling products on the web is that it is self-service. The customer has to be able to figure out how to buy the item by themselves at 11:00 on Sunday night. Options should be easy to understand.
A tshirt has easy to understand options: size, color, design. Complex options or options contingent on other options will cause the customer to call with questions. It is ok if your product or service is complex. Just post a toll-free phone number and your hours of operations on your website. Then, the nice thing about talking to your customers, you can figure out what they want better and upsell them into better products.
Sometimes the best way to handle complex options is to have a quote form. The customer fills out the form, you reply to their email with a quote. Then you can ship it out when they accept the quote.