Poor little dog. Yes, it will likely be expensive. Many Vets will work out a payment plan for you. If you let it get worse it will be more expensive.
If it is IVDD you're already doing things wrong. She needs exercise to keep her back muscles strong. You need to know what kind of exercise she can do. You need to know Where in her back it is so you can help her properly. Meds will releive pain AND reduce inflamation.
That's what I learned when my Lab had an acute espisode of pain and was found to have both IVDD and significant spinal spondylosis. A wrong move by me could have moved her past the point of return to health by medicine to the point of needing surgery.