I had somewhere between 16-20 ultrasounds. I had a high risk pregnancy and they were keeping a close eye on the baby. Each ultrasound cost around $700 plus the costs from the doctor and lab for reading the results. Luckily our insurance picked up the cost after we paid $2500 out of pocket. Even with all that expense my daughter was totally worth it and is perfect.
Part of the difficulty in answering this question is that depth and cause of coma may vary, and memory is impaired during coma so people might hear but not be able to recall what they hear. In brief: Hard to know. It is hard to know if people in a coma can hear you.
People don't remember things from being in one, so it'd be like he just woke up from a dreamless sleep, with the world changed. I've heard that 21 years is the longest time anyone has spent in a coma and was fully recovered. A documented case of a woman who woke up from her come after 20 years. http://www.cbsnews.com/stories/2005/08/0... the longest i've heard of is like 13 years or something close to that. but i'm sure there's longer.