There are a lot of sushi restaurants all over Lisbon. Sushi is so trendy now that I feel we have a sushi place on literally every corner. But not all sushi places are the same - Oh no sir! I've gone to many different ones, at different price points. Some are too cheap, and the quality is not that great... Some have amazing, mind-blowing sushi but will make a whole in your wallet. It took me a while to find the restaurant with the perfect balance quality/price but I thing I've got it!
It's called King Sushi and it's located on one of the main arteries of the city, near Campo Pequeno. It has a nice cozy environment, usually with some Asian music on the background. It's buffet style and it's not just sushi. They have Chinese food -- really good too! -- and a stir fry bar where you choose the ingredients and they make you food. It's really good to go with someone that is going to try sushi for the first time: they may not like it but at least they will have something else too eat! They make fresh sushi pretty much constantly, you can even see them preparing it, and if you want a specific type you can ask and they'll make it just for you!
As for the price, well it's 15.99€ + drinks for dinner (lunch is slightly cheaper). But it is worth the money. The drinks are a little bit expensive -- but if you want to get your money worth, ask for Jasmim Tea! You'll not be disappointed.