Statistics survivors, and good statisticians, have to ask these tough questions. Only a small percentage of customers may fit that description. Not that summary statistics are all bad. A mean gives you the arithmetic average. However, an income distribution can yield a mean much higher than its median if a few wealthy individuals are included.
Median income is often a more useful number because people are, by definition, closer to the median.
On the other hand, nobody may have exactly the median income, though it's still useful for comparing two distributions. The answer will tell you the base upon which the percentage was calculated. In tabular data, always look for the 100 percent column or row. Only then will you have a reference point for the percentages. In general, the smaller the sample, the larger the error term.