When this card was first announced the market has set a price of $50 a piece. In time it halved down, which is a more realistic price. If it shows good results in Standard and beyond, then it will rise up a bit again.
Nicol Bolas is undoubtedly very powerful, so it is definitely the safest investment one can make right now. Although the mana base is a bit awkward, which locks it to be played only in Grixis decks, it's still going to dominate that archetype.
Another possible scenario is that it will have a huge success in Commander format, which is a perfect environment for such powerful planeswalkers.