They are certainly similar in appearance to the Mossy but to my knowledge their internal operation is entirely different. To that end, it probably isn't the best comparison to use. I would suggest looking at them in comparison to Winchester Super X2 and X3 as well as Brownings as that is the operating system that they are based on. At that price point, they are very comparable. I actually purchased a gas ring to shoot ultra light loads that was designed for the Browning Gold and it works perfectly. Add in the fact that you can now do barrel changes with this shotgun and you have a much more versatile platform than is often found in the shotgun world.
In regard to price, yes they have come up in recent years but so has everything else. In addition, I have not heard of any problems in the manufacturing process like those that seem to have come up repeatedly with the Mossy 930 SPX. Quality control costs money, and that may go a long way towards explaining the difference in price in combination with what I feel is a smoother and more reliable operating system than the Mossy.
I should note that I am completely in the tank for this particular shotgun. I am at a thousand rounds now roughly and have not had a single malfunction. I should also mention that it is a bit like an AR in that it can be a money pit.
Since I have purchased it I have replaced the ghost ring and front sights with tritium inserts, added a nordic extended bolt handle and bolt release button, tapered off the fore grip a bit to make reloading easier, and put on a side saddle. All told I am over a $1000 at this point with the add ons. I bought it in 2006 when it did cost significantly less than it does now.
I am a person who does not mind spending a bit more for what I personally perceive to be higher quality. With all of my guns I would rather save a little longer and buy exactly what I want rather than what I can afford at that time. I do not make great money by any stretch so I try to avoid buyers remorse by making sure that I know exactly what I want and do my research so that I know how to properly judge quality.
That's just me, as always my opinion is probably worth exactly what you paid for it.