Hint, I didn't pay nearly that much. Thank you blue nile!
When did you buy it? What lab graded it? What are the cut/polish/symmetry grades? If its a round there are other things to consider? There are A LOT of different factors when determining the price of a diamond. Another thing to consider is the price of diamonds has skyrocketed by about 30% or more since last year because of a huge growing demand in India and China.
A E IF 1.3ct non H&A GIA excellent cut round goes goes for about $25k online right now, that would easily go for $40k at a retail store if you could find it. An E IF 1.3ct H&A AGS Triple 0 would be well over $30k online won't likely find it at retail unless at a independently owned highend/upscale boutique jewelry store. I base that on a 1ct F IF H&A is going for 22k and a 1ct D IF H&A is going for $36k. For shits and giggles a 2ct D IF H&A is going for $134k right now, a 3ct G VS1 is going for a $110k. I'd prefer the later.
Knock off about 30-35% and that would be what the same stones would have cost in late last year. If you bought a diamond late last year, or at the very beginning of this I would go get it appraised as your insurance policy probably doesn't cover it fully anymore.
Back to the OP. Some advice.
1. Cut is king, not size. My fiancee gets far more comments on her diamond than people she's knows with diamonds that are quite a bit larger but of lesser quality. Hers is a sparkly fireball in almost all lighting, theirs are lifeless in in comparison. There is a lot of stuff to learn. I'd say learn it.
2. Look at retail if you need to, but never buy retail. Buy online and go with a place like GoodOldGold(someone that specializes in cushions) if you are going with a cushion cut. If you were going with round. Hands down I'd go with Whiteflash.com or BrianGavinDiamonds.com. Winkjones.com is another good one, but I have never bought from them. None of these vendors will steer you wrong.