All vets vary on pricing but my friend had his dog put to sleep at a 24hr emergency vet's office and it was around $120-130.00 this included disposal of the body also. Also his dog weighed a little over 100lbs ( price may also vary based on weight).
To get to keep ashes with or without urn is extra also if you choose to want this service.
Also I think if it's by appointment at a non-24hr vet it would be cheaper too!
Sorry to hear that your dog needs put to sleep. God bless you and your dog.