I completely and totally disagree on a couple of levels. As someone who supports Saga, I want the book to continue and the best way for that to happen is for as many people as possible to pay for the book. If that means that they are buying it via trade, comixology, etc., whatever. Brian and Fiona will keep writing and drawing the book as long as they continue to make a living off of it. The longer the run is, the better it is for the value of what you own.
Also, trades create more customers for the books. Think about the Walking Dead. Even before the show or rumors of the show, a lot of people jumped on board the title because they picked up the trades and loved them. This created demand for early keys... before the show. This can and may make the Saga books that you own more collectable.
In sum, more readers = more value for your earlier issues, in my opinion. Reprints and trades help create more readers.
+1
I love Saga and I had a friend ask me about a month ago (or just when #7 came out) what I would recommend adding to his pull list (I had already got him on the Revival and Bedlam wagon). I said.... SAGA! He went out and bought the trade + issue seven and is hooked.