I don't think this stone is worth rap +4%...
I wouldn't buy any stone in excess of 0.5 carats without some form of scope analysis, or at the very least, gemcalc, sarin report or something similar. If it's a >20k stone larger than a carat, I'm definitely not parting with my money on that photo alone with the GIA cert.
I believe you can get a similar carat weight diamond at JP for that amount of money. Based on a simplistic price per carat calculation using smaller stones in the same rap weight band, I think a G VS2 of that size should be around 18k, a D VVS2 uplift maybe in the region of 24-25k. Since you are looking at value for money, consider a F/G VS2 stone, I think that should be comfortably below 20k excluding setting, 20.5-21k with setting.
EDIT: Just did a quite check on my usual Whiteflash reference prices - they have a number of A Cut Above range diamonds within your price range with carat sizes between 1.30 to 1.36. If I were you, I would be a lot more inclined to consider those if you want to buy online.
EDIT 2: Since you're after a larger stone, I checked out the Crafted by Infinity diamonds at High Performance Diamonds as well (which IMO is the best cut quality you can get for an online retailer, with a price premium to match), and they have a 1.33 G VS1 in your price range as well.