Hi, I'm in California too. We had a very thorough round of bloodwork done for one of our dogs recently that was listed as a "senior panel" which included thyroid readings and lots of other stuff. That package of tests alone was $230. Tack on some sedatives (which were absolutely needed to get that blood from my dog), some other tests to rule out other problems, the consultation fees, etc., and yes, we easily saw a $500 bill. Without X-rays. For a relatively young dog.
I've learned that vet bills can and do get REALLY expensive in this state.
And I think once dogs get older, some increased level of medical maintenance and expenses is to be expected. You can't really avoid the fact that your pet is getting older, but I think you can work with your vet to establish a plan of care that would work for your budget. I don't think you should be expecting to pay $1000 or jump to X-Rays immediately. But yes, ruling out a urinary tract infection sounds like a good start.
Not sure how your relationship with your vet is, but I've learned that it's worth it to shop around for a vet that you do feel comfortable with. Yelp.com, for all its issues, has helped me navigate the local vets, as well as talking to other pet owners whose opinions I trust.