Logos version: Nestle-Aland Greek New Testament, 28th Edition, with Critical Apparatus -pre-publication price US$70, still a bit too expensive...
Critical Apparatus only: US$50
Note: the SESB v.2, The Stuttgart Electronic
Study Bible -with apparatus of both NA27, BHS, LXX and BHQ [Minor Prophets and Proverbs], is now on sale: US$130. See review here.
For me, I will wait for the SESB v.3...