How can I quantify the business value of normalization?
The actual costs are difficult to quantify as they are often diffused.  Often they appear as slower transactions.  For a system used rarely, this may not be significant.  For a system used for an hour a day, that is taking twice as long as is required the cost would be about 100 hrs a year per person using the system.  Slower transactions may also have higher error rates due to users being distracted or interrupted while processing transactions.

Failure to normalize the data often results in in consistent data through-out the application.  Updates to some records may be missed, or incorrect records may be updated.  Inconsistent data can have serious business and/or legal implications.   Such problems can reduce the reputation of the business. 

Updates to non-normalized records may take many times longer than with normalized data. (That is time someone is waiting for the system rather than moving to the next task.).  In some cases the update will fail, or lock the table for excessively long periods of time.