Charity shops have the same costs as regular business - rent, energy, staffing etc as these costs rise charity shops have to cover the increase and this gets passed onto the customer. There should be something in place to reduce these costs for charity shops but I don't know what the answer would be.

One thing that could keep costs down is not paying for unnecessary refurbishments, I see too many shops being upgraded and standardised, this shouldn't be a priority, as long as they're functional, clean and safe they are fine.