$700 sounds reasonable...

Water causes the stones.
 

I have asked my Doctor (Human Doctor) He advised me, to give my Duchess bottled purified water, this will cut the chances of stones by at least 60%, moreover, the Doctor suggested for me to install an under the sink Water Filtration System in so all of us can drink from, Humans & Dogs. I actually have the under the sink filter already, What I do now, is I get my potable filtered water from my under the sink filter and then I pour it in a BRITTA and the results are even better than bottles from the grocery store. My water now is double filtered. So let's see if my Duchess will ever get any stones.

First of all, it's important to find out what kind of stones your baby is producing. It is absolutely Necessary to have the stones/crystals analyzed to find out the type. Please ask your vet to do this. Also, it's important to find out your dog's urine pH. The type of stones/crystals and pH will completely determine *which* prescription food your dog needs.

The treatment for different types of stones are completely different from each other. In fact, if you treat for struvite stones which form in alkaline urine and your dog has ammonium urate stones, then you are going to have more problems...

I used to juice half a celery stalk or half of a zucchini everyday for my yorkie who has a severe history of stones.

If you are feeding dry food, it is absolutely necessary to add equal parts water to the food. So, if at each meal your dog gets 1/4 cup of dry food, then you need to add at least 1/4 cup of water to it each time.

The important thing here is to get as much moisture in your dog as you can because if you dilute the urine, then it will keep the stones from forming.
You can also give high moisture treats like seedless watermelon and skinless apple pieces (no seeds).