Too expensive seems odd to me, you pay 100k IP and you can get 5x item to make 5x talisman with it (so it's 20k IP +10M for each 8H talisman). I think for every person in game with normal gear this is possible to get this. Even if you only do daily 5 stages of inter, you can still get enough IP to get the 8H talisman everyday. You can also simply farm any monster in the world, open the boxes/sell the boxes and use money to buy IP. 300K IP is pretty cheap and will last you for quite a while. Time boxes also grant IP tickets.
Spirit stones are also very cheap, the price does not need to be adjusted. Just do daily 5 stages of inter and hope you hit 100 or 300k IP ticket. hitting that every once in awhile will give you enough IP to do w/e you want basically.
Have not seen a transcended sage weapon/armour, not sure if it's even possible. Sage weapons/armour are valueless with all the new gear that released, it really isn't worth transcending if you ask me (if it's even possible)
It's still in the alpha phase, things might change (when progressing to beta and finally the final implementation), the duration might change as well. I think at the moment they want to see what the community thinks about the talisman, if most people like it, they will probably release one that lasts longer and maybe different ways to obtain it/buy it as well.