How to determine if Standard Deviation is high/low

If you take your cues from the financial industry, you can use the coefficient of variation (CV), which is the standard deviation / mean. This formula is used to normalize the standard deviation so that it can be compared across various mean scales.

As a rule of thumb, a CV >= 1 indicates a relatively high variation, while a CV < 1 can be considered low.

Some references to usage as "rule of thumb"