A quick google search will introduce you to a number of other rules for buying engagement rings. There’s a so-called rule which states the buyer should spend the same amount as the initial purchase on his or her car. Others use the age of the person being proposed to, stating that if your partner is 32, you should be choosing a 3.2-carat ring. More shockingly, there are some who say the ring price should match how ‘attractive’ your partner is. Clearly, these made-up rules are not worth your consideration. More importantly, they aren’t based on anything other than hearsay. So, the best engagement ring isn’t always the most expensive. And a cheap diamond engagement ring bought online can often be of better quality than one which is store-bought. . Harry Winston diamond rings for women feature brilliant diamonds and vibrant gemstones, and are available in platinum or gold.. $500,000 Harry Winston 4.59ct Round Baguette Diamond Platinum Engagement Ring 2 tapered baguette sides, both original from Harry Winston. Ring has original Harry Winston appraisal papers, and GIA certificate with box..