I'm not sure if it's less expensive or not but Royal Canin makes a similar type of food for struvite crystals. I currently use the Royal Canin SO Formula which prevents calcium oxalate crystals and dissolves struvite crystals. It also makes your cats drink more water so they also pee more often. So far it's keeping all of my cats healthy. Different vets may also charge different prices so you may want to call around. Good luck.

Here's the link: http://www.walthamusa.com/Learning%20Center/SO30.html.