You must have heard of some noob complaining about whether to use "big bones" or "dragon bones" or maybe even "frost dragon bones" to train prayer. Or a person not knowing whether to high alch cheaply or go with the faster, yet more expensive method of stringing amulets. This guide aims to help you figure it all out.
What is Time Value Cutoff?
The idea is this. Suppose you decide to do a slower, yet cheaper method to train a skill. Each extra hour you spend there, training away, with your slower method versus the faster method, is one hour you could have spent directly trying to make money. And if you know how fast you make money in an hour on average, you can calculate which method is for you.
Note: The prices of items fluctuate a lot on the Grand Exchange. Also, at any given day, an item may buy only at way below or above the GE trade price. Be wary and always use a calculator. Google has a good calculater. Just pop in queries like "500 x 500" and hit search.
Step One - List Your Goal and Assumptions
Goal: Get 5,000,000 prayer xp
Options: Big Bones, Dragon Bones, Frost Dragon Bones
Method: Gilded Altar
Bones per Hour: 1000
Big Bones = 328gp each, at 52.5xp each
Dragon Bones = 4,468gp each, at 252xp each
Frost Dragon Bones = 16,000gp each, at 620xp each.
What I will calculate: Which bone to use.
What I will NOT calculate: Whether to use gilded altar or ectofungus. That's another TVC problem. This example assumed you use gilded altar to train prayer.
Step Two - Find "Gp/Xp" and "Xp per Hour"
Big Bones: 328/52.5 = 6.25 gp/xp
Big Bones Xp per Hour = 52.5 x 1,000 = 52,500 xp per hour
Dragon Bones: 4,468/252 = 17.73 gp/xp
Dragon Bones Xp per Hour = 252 x 1,000 = 252,000 xp per hour
Frost Dragon Bones: 16,000/620 = 25.80 gp/xp
Frost Dragon Bones Xp per Hour: 620 x 1,000 = 620,000
Xp Needed: 5,000,000
Big Bone Method: 5,000,000/52.5 = 95,239 bones
95,239 bones/1,000 (Bones per Hour) = 95.23 Hours
Total Cost: 5,000,000 x 6.25 = 32,250,000gp
Dragon Bones Method: 5,000,000/252 = 19,842 bones
19,842/1,000 = 19.84 Hours
Total Cost: 5,000,000 x 17.73 = 88,650,000gp
Frost Dragon Bones Method: 5,000,000/620 = 8,065 bones
8,065/1,000 = 8.1 Hours
Total Cost: 5,000,000 x 25.80 = 129,000,000gp
Big Bones vs Dragon Bones:
88,650,000gp - 32,250,000gp = 56,400,000 gp
95.25 - 19.84 = 75.41 Hours
65,400,000gp/75.41 Hours = 867,258 gp/Hour
Thus the TVC compared to these two is: 867,258 gp/Hour
Dragon bones cost an extra 56.4m, but saves 75.41 hours.
If you make over 867,258 gp/Hour, you should use Dragon Bones rather than Big bones. But what about Dragon Bones vs Frost Dragon Bones?
Dragon Bones vs Frost Dragon Bones:
129,000,000gp - 88,650,000gp = 40,250,000gp
19.81 - 8.1 = 11.71 Hours
40,250,000gp/11.71 Hours = 3,437,233 gp/Hour
Thus the TVC compared to these two is: 3,437,233 gp/Hour
Frost Dragon Bones cost an extra 40.25m , but saves 11.71 Hours,
If you make over 3,427,233 gp/Hour, you should use Frost Dragon Bones rather than Dragon Bones.
TVC for Dragon Bones vs Big Bones is 867k per hour.
TVC for Dragon Bones vs Frost Dragon Bones is 3.43m per hour.
I wrote this guide because I hope some people would appreciate turning Runescape into a more mathematical endeavor. However, you can always decide to play Runescape however you want to play it. After all, that is the CORRECT way to play it. TVC does NOT calculate how boring or clicking intensive something is. Whether the extra efficiency is worth it for the boringness involved is up to the reader to decide.
Now we consider that all things in Runescape can be expressed in TIME, the reader might notice that all xp earned on Runescape may be put into "time". For example, if the xp/hour for training runecrafting is at 40k per hour, we can say that each runecrafting xp is equal to Money You Can Make Per Hour/40,000. In this concept, you may find that Herblore really isn't that expensive anymore...
If you spot any mathematical errors in my guide, please let me know. If you wish to repost this, that's ok, just put my name in there somewhere. Other than that, let the comments roll.