Updated info for the villain path.
The tasks will allow you to complete pages 1-6. If you don’t have time to finish the tasks you can use the purchased points to redeem some of the rewards on pages 1-6. Page 7 is for any points you bought but didn’t need to finish pages 1-6, so you can recoup some of your moonstones.
You can buy one set of 100 villain points at a discount (costs 800 moonstones instead of 1000 to get 100 villain points) to gain back an additional 100 moonstones.
You can redeem the 100 points for 900 moonstones on page 7 (only up to 10 times), which gets you back 100 more moonstones than it cost you. This only works once (because of the discount), then it ends up costing you more than you get back.
Villain points are worthless after the star path is gone I believe. I think anyone who made the mistake of converting more moonstones into pixar points just lost the moonstones and the points. So it’s a waste to spend more moonstones. Hoard the moonstones.
To maximize your return on investment and minimize the overall moonstone cost, the most you should spend on the villain path is 2500 moonstones for the premium path and an additional 800 for the page 7 rewards. Do all of the tasks and you will recoup almost everything you spent. I finished the path and think the net cost was around 300-400 moonstones.