I have to write a letter about a price increase but in the same letter I want to thank them for their support please help

I would be brief and to the point.

'Due to cost increases beyond my/our control I must also increase my price/s. The same quality and attention to detail will be offered. We have minimized these costs as much as possible.'

If possible you can add a feature that will not increase your cost/s but will be of value to your customers.

Stringer