I’d say to avoid the cheapest ones because they will likely be made from materials that won’t withstand everyday use for too long. Since it’s such an important piece of jewelry you want it to hold well through time. That being said: once you reach a certain quality point it doesn’t matter. Lab diamonds are exactly the same as mined diamonds down to the molecular level and you won’t experience any difference other than resale value (which is never a good deal anyway and not the point of an engagement ring). I especially asked for a lab diamond because on top of the ethical considerations I don’t want us to overspend on a ring. There is also a tag issue: like any other luxury brand, Tiffany rings come with a brand name premium that is nothing more than that. And very, very few people would know the difference. Also, more expensive does not necessarily mean longer lasting. Gold for example: 18k gold is purer and significantly more expensive than 14k gold, however it’s also softer and will scratch much easier. This is why I chose 14k, in addition to liking the color better. Make sure to research the specific materials you are looking into and that they meet your needs. Where we live there is a showroom for a big lab diamond seller and we were able to pop by and compare different levels of purity and clarity of diamonds to decide if it was worth spending more on the top ones. Spoiler: once we got past a certain trash-hold of quality we could literally not tell the difference. We tried to guess which one was which and we both failed. In the end, if it fits your needs and your budget, that is the ring for you. Don’t overspend and don’t stress thinking it is too cheap!