Keith,
The parts for the Webasto burner are German design and made and you do pay Mercedes prices. It is a company with a captive audience, being a unique burner, and there are a lot of expenses and extra profit added in for all the companies in the chain that sell, import, and resell again here in the states. It is also a low volume set of items. Once in awhile you can see some parts on Ebay with a lower price but you may not get the quality part that you are looking for from that source. I also think the Webasto parts are extraordinarily over priced for what they are. The two parts that you should be able to find decent priced sources for are nozzles and filters. Those have U.S. company and individual sources that compete but the era of the $4 filter is probably behind us unfortunately. If there is a reasonable priced source, I have not found it, that being said I am happy that we can get the parts rather than the company going out of business.
Later Ed