You can re-price kitsets in bulk by a percentage, but only if:
All kitsets are set to have the pricing method as “Product Group Markups” under the Products / Pricing tab
All kitsets are set to a specific product group that is valid
The Product Group needs to have an active markup (Admin / Settings / Manage Product Groups > Markups tab – make sure to have the box active ticked)
The settings above mean that all Products belonging to the Group created will have a price according to the markup that has been activated for each price level, and because these are kitsets, then the basis it will use as cost to add the markup will be the sum of the cost of all components on the kitset.
Be aware that if you use the recalculate kitsets tool (Products / Recalculate Kitsets), you will be updating the costs and the system will give you the option to update the selling prices or not.