Why Lifetime-Value-based Pricing Just Plain Rocks
what does "Plain Rocks" mean?
Basically means "is awesome"
Why Lifetime-Value-based Pricing is awesome
"Plain" isn't really needed here and is just used for emphasis. "Rocks" can either mean the actual geological object or as a synonym for awesome, amazing, etc.
To say that something "rocks" means that is is cool, awesome, fantastic, etc. This comes from rock-and-roll music, where "to rock" (to play or sometimes listen to rock-and-roll) because synonymous with being cool, awesome, etc.
The phrase "just plain X" is an intensifier; it basically means that there are no catches, drawbacks or downsides. This comes from the meaning of the word "plain" as "simple, unadorned, without extras".
So "just plain rocks" means "is awesome, with no downsides".