What a lovely idea. As you may know, diamonds are priced by the 4 Cs - Carat (weight), Colour (lack of yellow/brown with the closest to white being D), Clarity (flawlessness), Cut (proportions and light reflection). Diamonds hold their value well, so it's a good investment, if purchased with care. It's silly not thinking about them holding value. If you really don't care, buy some costume jewellery or lab grown diamonds. But I think that's rather defeating the object. Diamonds are affordable, it is just a question of finding a pair that is priced correctly for you.
In terms of pricing, you are mostly paying for a brand name if you purchase from say Mappin & Webb, Tiffany, De Beers etc. Your best bet is to go to either Hatton Garden if you're in London, or else a local jeweller who specialises in gemstones. You will definitely get more for your money if you take your time to find the right person to guide you. Knowledge is everything, not only theirs, but yours. By this I mean not just looking at the stones, but trying them on and working out what colour/cut you like on your ear lobes, but how you feel in them. Some prefer tiny chips, others like a larger stone. Some a classic round brilliant cut, others emerald cut, ad infinitum. There are lots of shapes available. The only way to decide what is best for you to go and try them on. And, once you start looking in person, your eye will adjust and begin to tell the difference in quality, particularly in terms of colour. I say this as someone who has always been interested in gemstones, and during a sabbatical of sorts, gained a certificate in diamond grading from Gem-A.
On my part, I have a pair of diamonds studs set in platinum, each around a carat each. One is slightly over, one slightly under. The colour is F, and a well-matched pair. Very few inclusions, one is a VS1, the other VVS1. The stones were purchased by my mother in Amsterdam in the early 1980s, and set by a jeweller in London. She wore them every day for almost twenty years, and I have worn them pretty much every day since she died. They make me feel dressed (and v. special). They're not ostentatious, in fact, I sometimes wish they were a larger carat!! Unless someone knows what they're looking at, you might not even think they're real. Have worn them everywhere and never once felt unsafe in them. Since I started wearing them, I rarely wear anything else in my ears. I love them and are thankful to have them as there is no way I could have afforded to buy them (or something remotely equivalent) myself.
PS. They are regular butterfly backs and have never had lost one. But then I do wear a small plastic back as well as the platinum butterfly back.