Medically, the consequences of not replacing missing teeth include unwanted and unhealthy nutritional changes. There are also potential risks of diabetes, obesity, heart disease, depression, and an increase in the likelihood of developing cancer. These are all prominent health risks that are avoidable by providing a dental structure with partial dentures or another quality tooth replacement option.
The reason the cost for either "new" (conventional, non-immediate) or "replacement" full dentures is the same is that for the most part all of the steps that the dentist must take, and the number of appointments needed, are essentially the same in both cases. Also, all of the costs they encounter (like the price they pay a dental laboratory to fabricate the appliance) are the same too.
Later that afternoon I came back to have 16 teeth extracted. I got to the office and waited about 30 minutes before I was seen. I got to the back and began injections. After this I went to a full blown panic attack and came close to passing out. The one positive is the dentist who was working on me took it in stride. I wasn't treated disrespectfully and after about 30 minutes the panic subsided and she was able to finish my injections and begin pulling teeth.