I have a client where about 40% of his products (around 1500 of em) can be customized in various ways, from imprints to sizes to colors to fabrics to options, and a lot of those options entail a product price change (some entail a shipping charge change because they add to the weight) We're still grappling with how best to do this, both from a user experience and not to mess all over ourselves in the search engines.
Long term, the idea is to combine as much information as we can into as few pages as we can and still make it useful for the consumer. We don't have a shopping cart solution that will handle everything out of the box, so custom programming is going to have to be done at some point.
Right now - all the easiest products are being combined onto a single page where it makes sense to do so.
We're working on a "widget-builder" customization tool where the customers can see their widgets every step of the way as they choose sizes, colors, options.
Some "brand builder" products will have adjunct information pages, where people can get FAQ or support info, customer success stories, application ideas, etc.
That's about as far as we've got. Is a puzzlement for sure.