A real partial or implant retain partial is the most economical and long lasting treatment of choice. In a bridge, you will need at least seven units bridge and this bridge will go across the curve from posterior to anterior teeth. Before you plan to go any further, please find out if you can keep the remaining teeth for life. So sad that many people spend all their money into a prosthesis, then found out that other teeth will begin to have the problem within few years. The real question I would have ask is why do you lose all these teeth and is there a plan to prevent any further loss? Only then I will replace these missing teeth. About these plans, what I have seen in the common practice that these office will manipulate the insurance plan to get what they want in their fee, NOT abide by the fee contract. Similar to many department store sale, they raise the price up then discount them down, or they sell the price of the shirt low and increase the price of the pants. Concentrate on the warrantee of the work, look for the answer, not the price quote. Full mouth evaluation is very valuable in treating this case.