That's sounds about right Dien.
I signed up for one through
http://www.dentalplans.com about 2 years ago when choosing a new dentist and the savings was amazing. Cost like $100 for the plan and saved me over 7k according to the prices I was given.
Of course I think their standard prices are heavily inflated to profit from those with insurance to cover the costs - but those without ins or a savings plan like this pay through the nose and that rubs me the wrong way.
Good luck starting a new plan here. I wouldn't say it's impossible, but it'll be tough with other bigger players who have already been in business for years. You'll need a great reason WHY dentists should signup with you.
Personally - I think it would be easier for you to develop and promote a local lead generation website and then "sell" these leads to the dentist. On average a new client that stays with a dentist for a few years has to be worth thousands - so you could probably get at least a few hundred for each new client you can supply.
HTH,
Steve