over the years and miles.
However, I can't recall the costs of the panels or other similar items other the front air dam of the 996 cost around $300 (with a PCA membership discount). The other plastic panels/items for both cars were a lot less, with the most expensive one probably less than $150. Course some of these I bought some time back so prices could be higher.
Hate to mention it but one large one I bought for the Boxster years ago but to this day have not yet installed it. The old one is while a bit damaged holding up ok, good enough I guess. The techs have told me when I bring the car in bring the panel in and they'll install it but I keep forgetting to dig the thing out of the closet.
For the best info in prices visit your local Porsche dealer parts department and get a price for the part or parts you need. If you know the part number perhaps you can then look the part up at one of the online sites for a price as well.