I do conference and restaurant chairs on a regular basis. If they are draylon then £4 each. Will clean really easy, pre spray 10 or so with a m/s, pureclean or ultimate master. Quick brush over and clearwater/acidic rinse with low pressure. This will make the draylon glow and look really nice. Wipe legs/frames down with a towel, buff and dress pile. 20 an hour hwe.
Just a small point check the fabric. Some group 'it's like draylon' along with viscose
Do a water test on the underside, wet the pile, dry and test for stiffness. If the fibre springs up nice and bouncy it's fine. If it mats together it will require a quite separate technique and you will need to charge a lot more.