Reputable Russian 000 Beluga is about $100/oz or $4k/kg; Iranian 000 Beluga is more like $175/oz, $6k/kg. I think you'd have to be crazy to buy that stuff these days, since so much of the market is controlled by crooks, so who knows what you're actually getting? You can get Russian Sevruga for about $45/oz, California White Sturgeon (farmed) for maybe $30/oz. Decent Alaskan Salmon roe for $10/oz. YMMV, especially in a restaurant; a place like Caviar Russe on Madison and 55th will sell you a little under 2 oz (50g) of 000 Beluga for $425 or an ounce each of 000 Beluga, Osetra, and Sevruga for $440.