Southperry's own Thief Flaunting thread =D

Supposing regular enhancements:
1 Star: 80% = 1.25 protect scrolls.
2 Stars: 70% = 1.42 protect scrolls
3 Stars: 60% = 1.66 protect scrolls
4 stars: 50% = 2 protect scrolls
5 stars: 40% = 2.5 protect scrolls
6 stars: 30% = 3.33 protect scrolls
7 stars: 20% = 5 protect scrolls
8 stars: 10% = 10 protect scrolls.

That's per star on average. Add it up and you would have to get about a minimum of ~27.16 so about 28 total at about 5k each is like 135k NX to get 8 stars.

Good luck.

135k NX really isn't a whole lot compared to what a lot of people, yourself included I'm sure, have spent on cubes.