Since I play badminton the prices of feather shuttles increase by around 50 cent to 1€ per tube per year. I don’t know how much string people use, here yearly to complain? I doubt that many people could be more fussy than me with jobs. I go through a reel on own rackets per year.
On customers I increase the prices 3 times since I string based on the increasing prices of equipment. Always great for me because the most weird and strange people you get rid off and since I don’t live from stringing and got often too much rackets to do it’s win-win for me.
Customers can also buy their own string and provide. They pay reel price/20 material price at me, grommets included plus labour. Most people complain about club stringers because they forget the prices at local shops. I wouldn’t panic to increase prices.
We also have higher prices on grips (I’m also fussy with grips). IMO it is exaggerated to complain here about string prices specific when everything gets more expensive in badminton and to be honest: I love badminton more than I could even bother and also my clubs raised the price of membership. 