(CBS Local) — A revolutionary treatment that aims to cure a rare form of inherited blindness has been given a jaw-dropping price tag of $850,000. While the staggering cost may be hard to bear for some patients, medical analysts are actually saying the price of the treatment is less than expected.

Spark Therapeutics’ new gene therapy, called Luxturna, was reportedly lowered in price from $1 million after health insurers voiced concerns about their ability to cover the expensive treatment. The one-time injection will cost patients $425,000 per eye and reverses the disease called retinal dystrophy. The condition is an inherited mutation of a non-working gene called RPE65 from each parent.

“Many were anticipating this was going to be over a million dollars because it’s a small patient population,” Steve Miller of Express Scripts told Forbes. There are only about 1,000 cases of retinal dystrophy in the U.S. currently. “To be very frank, they’ve hit on a responsible price. Is it inexpensive? Absolutely not. But it’s responsible.”

Express Scripts Holding, which manages prescription drug benefits, is now working with Spark to create a new and innovative payment process for patients needing Luxturna. Unlike other drugs that are charged per pill or per injection, the one-time treatment of Luxturna has forced its makers to design a payment plan system for customers and insurers who would be overwhelmed by the $850,000 bill.

“It is the first gene therapy to come to market, so not only have they innovated with the science, but working with us, we’ve innovated in the payment models,” Miller said, via The Washington Post. The FDA approved Luxturna’s use in December as the new drug joins the list of other costly gene therapies – including Kymriah ($475,000) and Yescarta ($373,000) – which both treat blood cancer.