What is the difference between "valuable" and "invaluable"?

'Invaluable' = extremely valuable; valuable beyond measure.

Thanks!
But I still wonder it.
For example, there are words "distinct" and "indistinct" and those definitions are different.

Is 'invaluable' an exception of 'in-' prefix?

There's also flammable vs inflammable. Sometimes words outgrow their affixes and assume incongruous meanings.