How much is a jewel?

I'm curious, how much would one typically pay for a jewel? I understand that the price can vary greatly depending on factors like the type of gemstone, its quality, rarity, and even the craftsmanship involved in its setting. But could you give me a rough estimate or range of prices for a basic, yet still valuable, jewel? I'm looking to invest in something that can hold its value over time and perhaps even appreciate in worth. Thank you for your insights.