You're right. Here is the official statement on online.midwestern.edu
It says nothing about being free. It could actually be cheaper at your school. I would definitely call.
"Midwestern University has contracted with Sonora Quest Laboratories in the Phoenix Metropolitan area to facilitate this process and minimize your expenses and also to assure that the correct tests are done. If you wish to take advantage of our discount with Sonora Quest Laboratories, you will need to come to the Office of Student Services to pay for the titers and obtain a requisition form. The university provides a 2 week grace period following the start of classes to allow you to get these titers drawn. The expense of the blood titers will also be included in your financial aid package, which you will receive the first week of classes. We recommend that you wait until you have received your financial aid disbursement before you have your titers drawn. Again, you must come to Student Services first in order to take advantage of the discount."