Yes, there are two good auction houses which have several auctions a year specifically in war medals from various periods, including WWI. Spink in London at 011-1-71-747-6835 and Sotheby's also in London at 011-1-71-293-5000. Note that medals differ greatly in value based rarity, condition, and provenance.
The ehrenbecher cup is slightly afield and you may want to check with Stephen Maycock at Sotheby's whom you can reach by email at
stephen.maycock@sothebys.com.
They may not have a lot of time for a queery. However, if you want to pursue the field, then you should get in touch as they can tell you how to order auction catalogs and so forth or find them on the web.
You may want to also look at John Taylor's article "The Medal Collector and Selected Medalic items of W.W.I," page 39-46, Vol.31 no.1 2000 Cross and Cockade International, which you can order through their web page at
www.crossandcockade.com.
Best of luck to you. You might enjoy my small collection of "aeronautica" 1914-1918 at
http://charlesgosse.home.mindspring.com (no www). No medals but bits and pieces of old aeroplanes and so forth.