I would work closely with your veterinarian for the best results.
I would not make drastic changes in diet with a senior dog. It will have no effect on hip dysplasia and may result in gastrointestinal upset and more vet bills!
Also, glucosamine is a supplement (not a medication) not all supplements are benign.
http://skeptvet.com/Blog/?s=glucosamine
If the dog is experiencing chronic pain obviously you can not increase exercise, etc.
Decreasing intake may not be a good idea either. Seriously, have your vet call you back when he has a minute, discuss your financial concerns and see what he recommends.
Best of luck.
https://www.canineortho.com/index.php/treatment-hip-dysplasia (excerpt from article below)
Canine hip dysplasia that results in chronic pain and interferes with an active lifestyle is best treated with surgery. Four surgical options exist:
Juvenile Pubic Symphysiodesis (JPS)
Double Pelvic Osteotomy (DPO)
Total Hip Replacement (THR)
Femoral Head Ostectomy (FHO) – FHO is best suited for cats and small dogs (5-30 pounds). FHO involves removal of the ball from the ball and socket joint. Scar tissue forms between the remaining bone and socket (acetabulum) forming a “false joint”. The primary advantage of the FHO is lower cost, since no implants are needed.
The prognosis for dogs undergoing total hip replacement is good to excellent. Ninety percent of dogs are literally normal for life. There are no activity restrictions and because ongoing osteoarthritis is eliminated, very few if any require non-steroidal anti-inflammatory drugs (NSAIDs) like carprofen.
