So I was doing math to find out the value of Bond of Stone...

And, here's a spreadsheet showing the value of the mastery corresponding to the amount of armor or MR that you have (between 100 and 300 by intervals of 50).

It gives both the gold value the mastery and the stat value (armor/mr worth) of the mastery.

For example, if you have 100 armor and are not near an ally (2% damage reduction), the mastery is the same as having 9 extra armor, or 180 gold.

It shows the value for both the 2% reduction and the 8% reduction

Link: https://docs.google.com/spreadsheets/d/18TLMXwOvjM3GX4wsHMlFBP3rnGLRDMNxd5loQoz5_Co/edit?usp=sharing