In my experience none of those expensive products work. I have been trying to find a cure for my kp for 30+ years and this is what I find helps keep it at bay (95% gone) -
Gluten free dairy free diet - paleo gave the best results for me
Gentle exfoliation - I use an ameliorate mit (found the ameliorate lotion useless) and in the shower cheap exfoliating gloves with normal soap
Liberal moisturising - I use Superdrug vitamin e body cream. As it is cheap and comes in a big tub I am more likely to use lots of it and therefore get a good result. I have tried all the usual expensive lotions recommended for kp and they all gave inferior results to this cheap cream and usually smelled bad too
Sunlight. Nothing gives as good results as sunlight in my experience.
Honestly I've spent a fortune on kp treatments over the years, save your money and follow which of these tips you can instead.