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.
I went for a consultation and it took about 2 hours before seeing the dentist. I was taken in and a full lower x-ray was done, then the dentist came in and looked at it and we discussed my options. My teeth (only 7 left in my mouth) were so bad, that he decided I should go ahead and get a lower plate. He does not recommend a full lower, as there is always trouble with them. A full lower plate is a life changing event. You will not be able to eat any crunchy or hard foods. That's the truth. You will have to eat ground meats and soft foods the rest of your life. They will not tell you that, but I am telling you that.
Teeth can fall out for a number of reasons, ranging from genetics to drug abuse. Most commonly, teeth are removed or fall out on their own due to severe tooth decay. Neglect to upkeep oral hygiene or not seeking proper treatment for damaged teeth, can lead to the onset of decay which in turn leads to loss of teeth. Visiting you dentist in 6 month intervals is a good preventive measure to spot any early signs of decay.