Kind of hard to tell if the price is right without knowing more about the gun (model, condition). That said, $2800 is cheap for a Grulla (unless something is wrong with it). I recently bought a 3 year old 12 ga. model 216 set up as a Pigeon/Wildfowl gun that I used for ducks (including shooting 2 3/4" steel loads through with no problems) this season. I paid $5000 and although used, it is in like-new condition. I have one issue with an ejector sear on one barrel that sometimes uncocks when I fire it, but the only result is that it becomes an extractor for that shot. Someday I'll get it fixed. Fit and finish are as good as any gun I've seen and certainly as good as other Spanish Doubles.
Joe B