Their “Super Ideal” diamonds are just normal diamonds with ideal proportions and a HCA score of <2, which means they are well-cut diamonds. They are definitely not on par with JP Super Ideal cut diamonds and priced accordingly. Be careful cos some of the inclusions on their diamonds look truly terrible. Cut is not everything.
Like someone else suggested, you can take the GIA number of the diamond you’re interested in and get quotes from other diamond wholesalers for that same diamond. Alternatively, you could just try to negotiate with Fonder and try to get them to match the lower price quoted by other jewelers.
If you were planning to go the James Allen route, then going with Fonder will work for you. At least you can view the diamond beforehand at Fonder, pick a diamond with HCA rating below 2 and you can get a diamond that is reasonably well-cut and sparkly, and a bigger carat for your budget than you could get at JannPaul. But be careful with cloudy/milky diamonds (there are milky and faint brown diamonds on Fonder!!!! Need to read the report carefully), positions of inclusions that may risk the integrity (chipping) of the stone, and FLUORESCENCE. Sometimes you get diamonds at good prices at Fonder because they have fluorescence or other flaws like certain inclusions. This will affect the future value of your stone (undesirable, so lower). However, you will get a discounted stone, but be aware of why it’s discounted and what you’re buying. Faint fluoro is negligible but will affect the price and future value of your stone.
The BEST way to buy a diamond from Fonder would be to take the sarin report, GIA cert number of the one you’re eyeing and post it on Pricescope forum for the members to help you review the inclusions etc. I won’t trust Fonder or most jewelers to be 100% honest with you about every single possible bad aspect of the stone. But Pricescope will tell you for sure whether or not it’s a good stone and worth your money. No use asking us here, we only know how to tell you go to JP and buy diamonds cause you won’t ganna cheated (this is true cause JP is honest with superb customer service but a more expensive route to take because you can actually buy a bigger, still well-cut diamond at James Allen (or Fonder) for the same budget of a smaller Super Ideal at JP).