The Stargate franchise operates on a much smaller budget. They write their entire season with the budget in mind, so there's always three or four episodes intentionally written minus special effects (or perhaps shots that can be re-used).
Ironically, Firefly was never a big effects show, and the shots it had were almost comically sparse -- but effective for the show. The most expensive shots were location scenes with lots of horses, traditional gun battles, etc. When they were on the ship in space, those were the cheap scenes!
SG1 is also shot in Vancouver. Firefly ... in vastly more expensive southern California. X-Files NEVER would have been successful if it had started ops in LA. It only moved there after it had become a phenomenon, and the move to LA (in addition to silly ego battles with Carter, Duchovny, and Anderson) is Reason No. 1 the show went south.
Bottom line, I think, is Wheadon's heart really isn't into it. It's a battle he's already conceded and moved on (to Dollhouse). The only thing keeping this alive are the fans who discovered the series on DVDs and feel a bit betrayed they never had a shot to support it when it was on TV.
Yep when spending over 2 Million per episode the first thing people think is FX. The few episodes were we got to see several ships or city scapes, probalby blew through their entire FX budget.
I like so many others discovered the show too late. I had heard about it but didn't see anything on it until I read something. Then I was pissed that I had missed the start of it. Next thing I know it was gone. I was like WTF???