I will throw in my thoughts on this one, too.  As one niche in my Krag collection, I have a soft spot for different looks and types of sporters and cut-down Krags.  I have many different ones in my collection now and have bought and sold quite a few over the years.
Your gun here, while probably a good shooter and a solid hunting rifle, is not a lot more than that.  With the 03 type front sight, the pistol grip added in and nothing special about the cut of the fore-end, I would not pay the above-mentioned prices for it.  In my opinion, I would say that this Krag would sit more comfortably in the $150-$200 range.
As with any gun, what you can get for it quite often depends on who is looking for what at the time, how much they want one and how much extra cash they have at the time.

Best regards,
Tom