I have low testostone level test show there aroud 39. I know there are 3u different medicines I could get. Do you no the average cost for injections?

Choices. There are more than "3 different medicines" for testosterone replacement. See your doctor for an evaluation and discussion. The price depends on your insurance plan. There are also coupons and vouchers your doctor can give you depending on your situation. There are pros and cons with replacement. You need to find out why you are low first before treating. Do not jump into treatment..
Get checked. Before you start taking testosterone replacement, you need an evaluation by an endocrinologist to try to determine why your testosterone is so low. The endocrinologist can then define for you the different types of treatment options and discuss cost issues as well.