Ann: Burgundy starts work on polishing Fancy Colour diamonds, page-12

I was responding to the post from Vig009 and just suggesting that it was unlikely that their were a few million dollar diamonds and tried backing it up with an estimate. I have over 30 years experience in the diamond industry, specifically rough diamond valuations and have seen/valued more Fancy Yellows than most. For a 17.8ct rough gem quality diamond the polished yield is usually 30-40%, these stones look a bit above avg so could yield above 50%, it is rare to get a yield above 60%, so 10ct is near the upper limit, I have see not seen a million US$ Fancy Yellow, though there may be. More likely with Orange in the colour description, the diamond on the far left of the photo may be the most expensive. Pure Orange diamonds can be priced up to 500K range.
With Yellow diamonds there is no formal price guide as compared to Rappaport for white diamonds. You can look at what has sold at auctions or up for sale on certain websites though there can be some wide discrepancies, as secondary colours can impact price.
Supplementing your production with similar diamonds makes sense, though it is not without risk.
As mentioned by Fitzroy it is a chat/opinion forum!