Ditto the above
All sound advice. Your eggs should not be costing you that much for sure.
I personally swear by Dettol to clean the hen houses out once a week in the summer. I just give them a good scrub inside, into all the crevices and so on, rinse it all out and leave them to dry.
Also I was told many years ago to encourage earwigs to take up residence in my hen houses. They eat the red mite I was told. So I let a batch of them move in and before cleaning and washing out the hen houses make sure to remove as many as I can and pop in a jar and replace them back into their home corner once everything is back in place.
I've not had a redmite outbreak in any of the housing I use both the above in.
I also swear by old fashioned creosote (from agriculture merchants not garden centres). But often these days you cannot buy it without a licence or something.
I personally found Poultry Shield to be an expensive failure. Didn't stop or prevent an outbreak when I was using it. Hence me trying other alternatives.