What is the reason that your vet has prescribed the Urinary s/o for Benson?
Blue has been on Urinary Lp18 food for many years now for his Struvite bladder stones, the food helps to dissolve the Struvite gravel that can build up and it also makes him him drink more so he pees a lot and flushes everything through.
I can buy mine cheaper off the internet so my Vet price matches for me and I get it from him.
I'm now paying £62 for 14kg which lasts Blue about 12 weeks his price is usually £82 so it's a big difference.
May be worth looking at the price on the internet to compare prices, you don't need a prescription to buy it.