I have basic storage of 128 gb which I need to upgrade with 1 tb how much will it be ?

You could contact an Apple Service center and ask. I know places have started selling 1TB SSD drives for $450 and up (you install). My main concern is I don't know Apple's official state as to drive replacement and if they even do it. You must check first if it would invalidate any warranty you have if you were to do it yourself. You used to be able to self-upgrade all kinds of Mac components but Apple has really restricted that with newer Macs.

Last I heard, Apple uses a proprietary interface for its SATA-card SSDs. The industry standard mSATA and M2 cards do not work. OWC (macsales.com) is trying to find or manufacture cards that work in Macs to fill that gap. But the "opening the case of a Retina system voids warranty" remains an issue.