The cost of the work up is well spent if it includes an exam, blood work and urinalysis.
The blood work and urinalysis would help to differentiate the many causes of urinary incontinence.
Causes of urinary incontinence which increase with age include: Urethral hypotonia (also known as spay incontinence), kidney disease, urinary tract infections, pyelonephritis, diabetes, bladder cancer, bladder stones, other endocrine disorders (such as hyperadrenocorticism), behavioral causes and combinations of those listed above, and more.
A veterinarian cannot give phenylpropanolamine (PPA) if the cause of the urinary incontinence is not urethral hypotonia, since the drug can raise blood pressure and can be contraindicated if the pet has heart or kidney disease. That is why it is good medicine to have the blood work performed. There are medical and herbal alternatives to PPA, which would have to be prescribed by your veterinarian.
Many veterinarians are willing to work with their clients on the costs with a payment plan, Care Credit, etc. Maybe your vet will work with you too?
Until Dr. Cheng replies, I can tell you about my dog's similar experience. When dogs get old, sometimes the bladder and muscles lose their tone and ability to hold the urine. Sometimes a UTI will cause incontinence too, or a combination of both. The drug my vet prescribed is the decongestant phenylpropanolamine. It works well, but "speeded" the dog up too much so I had to cut the dosage in half. Her heart rate was way up there. I'm curious myself to know if there is anything else that works as well but with fewer "speed" side effects.
I don't know what part of the country you live in, but my vet did bloodwork, urinalysis and spent nearly an hour checking her out from nose to tail, and it was $95 including the phenylprop. and antibiotics. He's a fabulous vet too! We live in Houston.
To save your furniture, you might look into buying a pair of Hot Pants. They're made to fit your dog so you can insert a sanitary napkin to catch the spills. They have male and female versions too. A friend of mine swears by these when her rottie goes into heat.
A uti workup here in Southern California set me back almost $600. Ouch.