I am using an Ikea Vollmar ($250) currently (for up to 14h per day) and I like it. The back adjusting mechanism could be more fine grained. A few years ago I used a Vitra office chair, which was better and I might one day buy one. However, the price of ~1500$ is a bit hard to swallow and as long as I don't get back pain I will stay with my Volmar.