I would urge you to please reconsider going to this vet. If a real dental is more than you can afford please discuss a payment plan with your vet.
Both of my cat's have had dentals within the last year. They cannot know the depth of the work needed until they clean the teeth and take x-rays, and this is done when they are out.
I hope you reconsider and my best to you and Greylie.
Pam & Layla
Also, please, anyone reading this thread do not attempt a do-it-yourself dental on your cat. This is dangerous.