I think $90 estimates were too high, but OEMs last year leaking that the license fee was $80 for Windows RT and Office may have been accurate at launch. The licensing fees may have decreased to attract more OEMs as it started to fail.
As part of the 10.8" and under tablet licensing fee slashing the WSJ reported in March, some of the licensing fees are known. Windows 8 + MS Office Home & Student was $120 and is now "as low as $30". I don't see any quotes for what Windows RT + Office will cost, but it's probably in the same ballpark.
Even if ARM loses its efficiency crown and falls behind in performance, it still has many advantages. Price as you noted is one, but also nearly complete customization of the SoC's other devices (@ foundry of choice) is something Intel can't provide.
As part of the 10.8" and under tablet licensing fee slashing the WSJ reported in March, some of the licensing fees are known. Windows 8 + MS Office Home & Student was $120 and is now "as low as $30". I don't see any quotes for what Windows RT + Office will cost, but it's probably in the same ballpark.
Even if ARM loses its efficiency crown and falls behind in performance, it still has many advantages. Price as you noted is one, but also nearly complete customization of the SoC's other devices (@ foundry of choice) is something Intel can't provide.