Most people have the body pack style of receiver. It's nice because you can plug in any accessory such as a neck loop. Telecoil capability is built in. Some have a jack that can be used to support neck loops. A smaller room has a lower cost.
Volume is also a big factor.
If more infrared systems were sold, the cost would drop. You can set infrared up in a museum in such a way that the audio changes as you walk to different exhibits. It travels in a straight line. You can focus infrared to make it almost line of sight. But it reflects, so you can usually have it go anywhere in the room and face anywhere.