Tooltip readability - alternating row colors
When opting to show many custom and db prices in the tooltip, it can become difficult to differentiate all the rows at a glance, especially for wider tooltips.
One way of addressing this are alternating background colors for the rows of prices in the tooltip.
An existing example is the results window after any shopping search. The rows of auctions alternate between a darker and a lighter grey background.
Maybe a little something like this: http://imgur.com/a/2sxlJ
Custom tooltip text would be the best way. 3rd party tooltip addons can help