What is the justification for it costing $900?
Drug manufacturers don’t have to justify the cost of their drug to the FDA or the consumer. They charge whatever the market will bear. Manufacturers pay lip service to recouping research costs and high tech manufacturing processes but in fact there is little rhyme or reason.
If there were competition like in the automotive industry, I imagine prices would be lower. There’s simply not, in the drug industry. Each time a new use for a drug is discovered, the manufacturer can apply for a patent extension. Enbrel is probably about 3 or 4 years away from going off patent, so a new indication would give the patent holder another 7 years or so.