Giving your customers a good deal

Earlier today someone suggested that I read this entry from Cyrus.

As a performance guy people basically expect me to veto every new idea that might grow the size of anything anywhere.  I guess I surprise them when I don't.  The fact is that it's very hard for me to help make any specific decisions about specific features because only rarely can I assess the value of those features against their cost.  Instead I admonish people closer to the problem to do that analysis with questions like:

• Is this feature worth the cost? 
• Do you even understand the cost?
• In what dimensions will your customer see the cost?
• Will your customer think it's a good deal?

Sometimes I can help people understand the cost, for instance in Cyrus' case I'd be a lot more concerned about the CPU usage and working set of the new additions when they are idle than I would be about the disk footprint.  But what I'd really be interested in that cost/value assessment.  At what point would it have not been worth cost?  Was a quantitative decision made?

Accidental decisions are rarely good ones.