With the best-selling osteoporosis drug Fosamax on trial amid allegations that it causes “jaw death” in patients, you might think healthcare consumers would rejoice at the prospect of a new alternative to Fosamax on the market.

You might think that — until you look at the price.

The new drug, Amgen’s Prolia (denosumab), is up for approval by an FDA advisory committee this week. The aspect of Prolia that has received the most attention is that it is a product of biotechnology. It is a new class of drug, a “fully human monoclonal antibody” designed to target a protein that causes bone loss.

Studies indicate that it works as well as or slightly better than Fosamax and other bisphosphonates, such as Actonel and Boniva.

The Los Angeles Times reports:

The drug “does everything you would want a drug to do in women to prevent fractures,” said Dr. John S. Adams, an orthopedic surgeon at UCLA’s Geffen School of Medicine…

“This appears to be the most potent of the osteoporosis drugs,” [said Dr. Frederick R.] Singer … director of the endocrine/bone disease program at John Wayne Cancer Institute in Santa Monica.

That’s the good news. Now the bad news: the price.

Amgen, the manufacturer of denosumab, has not said how much the drug will cost, but analysts expect it to be at least $2,000 a year — and potentially much higher — and predict yearly sales of $2 billion to $3 billion.

Already, many insurance companies are pushing physicians to the generic version of Fosamax, alendronate, which costs about $100 a year.

Keep in mind also that, in all likelihood, insurance companies will not cover Prolia with a simple copay, but instead will require patients to pay for a significant percentage of the cost of the drug out of pocket.

The backstory here is that Amgen has been touting Prolia as a new “blockbuster drug” to Wall Street for some time now. And Wall Street has rewarded Amgen handsomely. As BusinessWeek reports:

Wall Street has set an exceptionally high bar for Amgen (AMGN)’s new bone-loss treatment. Shares of the world’s largest biotechnology company have jumped 27% in the past three months, to 60, largely on news of clinical trials that showed the drug is as at least as effective, and sometimes better, than standard osteoporosis treatments when it comes to preventing and treating dangerous fractures.

Wall Street is expecting a windfall, and Amgen will price Prolia to deliver that windfall. Which means the drug won’t be such a windfall for healthcare consumers.