Are there any legitimate reasons for a 28-300% variance in price? Why are discounts secret? I can totally see why the seller would want that, but these are publ

Are there any legitimate reasons for a 28-300% variance in price? Why are discounts secret? I can totally see why the seller would want that, but these are public health care countries studied and I don't see why public spending is allowed to stay a secret. Very depressing.