Here's a fascinating article in Scientific American titled
Why Things Cost $19.95 that discusses the psychological impact certain prices have over others. If you've always wondered why we see odd prices so often ($19.95 vs. $20.00), the article gives the answer. Two University of Florida marketing professors studied how consumers relate a ticketed price to the perceived wholesale "cost" of a good or service:
There were three scenarios involving different retail prices: one
group of buyers was given a price of $5,000, another was given a price
of $4,988, and the third was told $5,012. When all the buyers were
asked to estimate the wholesale price, those with the $5,000 price tag
in their head guessed much lower than those contemplating the more
precise retail prices. That is, they moved farther away from the mental
anchor. What is more, those who started with the round number as their
mental anchor were much more likely to guess a wholesale price that was
also in round numbers. The scientists ran this experiment again and
again with different scenarios and always got the same result.
Why would this happen? As Janiszewski and Uy explain in the February
issue of Psychological Science, people appear to create mental
measuring sticks that run in increments away from any opening bid, and
the size of the increments depends on the opening bid. That is, if we
see a $20 toaster, we might wonder whether it is worth $19 or $18 or
$21; we are thinking in round numbers. But if the starting point is
$19.95, the mental measuring stick would look different. We might still
think it is wrongly priced, but in our minds we are thinking about
nickels and dimes instead of dollars, so a fair comeback might be
$19.75 or $19.50.
I'd really recommend you read the entire article, but the initial takeaway for me is this: If you want clients to believe your rate (or set price for a given service) is close to your actual cost, price in odd numbers.