Sometimes an expensive office chair can be worth the cost especially if you need to sit for long periods of time and need a good quality office chair with good lumbar support.
If you sit at the desk in the office chair for 8 hours or more during the day then buying a good quality expensive office chair will do wonders for your back and overall body and improve your health.
Buying cheaper office chairs is sometimes a good idea but sometimes it's best to spend more money on the more expensive option for a quality office chair that will provide you with comfort and support for your back while sitting long hours.
A more comfortable office chair also increases your alertness and productivity because you're much more comfortable than you would be in a less comfortable chair.