You will certainly pay a premium for any product from Tiffany & Co. because you are buying into their branding and their heritage. Make no mistake--there is nothing "proprietary" about diamond studs--every jeweler has them. However, jewelry stores like Cartier, Tiffany, Harry Winston--etc all have quality standards in the diamonds that they use that you might not find at a typical department store. You pretty much never hear horror stories about people buying a piece of jewelry from Tiffany and finding out that it's below the quality that was described to them (the "I went to a jeweler and bought a diamond and found out it was a CZ horror stories" that you sometimes will hear about). Being in the jewelry industry for 25+ years--I can tell you that to some people---branding does mean a lot and they are willing to pay a premium for that branding. If your wife does value "branding"--just bite the bullet and get them from Tiffany.
If your wife doesn't really value branding--but just wants a nice pair of diamond earrings--I would recommend finding a nice independent jewelry store that has been around for a while that has solid reviews. You can either save some money by going that route--or you can get more for your money versus buying them from Tiffany. For the most part--I would avoid typical department stores as many of them basically use commercial quality diamonds in their goods. I'd also be very careful buying anything from the internet. I can tell you firsthand that jewelers/brokers in the trade will specifically market certain stones for internet commerce--and many of these stones are stones that don't live up to their certified metrics in person. You can have two diamonds that are both certifed as being the same color and the same clarity--and one can look beautiful and bright--and the other could look "sleepy". While they both look the same "on paper"--they are not worth nearly the same in the trade. The stones that don't live up to their metrics tend to go on the internet because they are hard to sell in brick and mortar locations where the consumer gets to te see the product before the purchase. This is why some people think that buying diamonds from the internet is "more discounted"--but in reality--it's basically paying lower prices for generally inferior products.
I will not use this platform to generate personal business--but I am happy to help in any way possible. If the OP wants some advice in regards to what he can expect to get for his budget--feel free to PM me and I can tell you what to expect/look for. That same offer applies to any other FBG. If any of you guys have any concerns regarding jewelry/watches---feel free to message me and I'll do my best to give any helpful advice.