A voc rehab assessment, plan and whatnot can easily run about $5k. They are low-balling you, especially if you are relatively young and/or have significant restrictions. Plus, if they agree to a voc rehab plan, they may be liable to not only pay for the retraining but also the time loss (basically what you were being paid while off of work). Are you employable at all, or just not employable in your time of injury job (or similar type of work)? Does your doctor support voc rehab? Have you talked to a comp attorney? And please do yourself a HUGE favor--make sure the attorney you talk to is well versed in comp law.
What are you wanting to re-train to become? How does that correlate to your education, prior work experience, interests/knowledge?
I ask this because if you have a back injury, no one is going to agree to a voc program to retrain you as a truck driver. If you had carpal tunnel, no one would pay for you to become a stenographer....see where I'm going.
If you're serious about voc rehab--hold out. Talk to an attorney. Be able to present your argument for at the very least a voc assessment.