Rewiring a kitchen is a big expense, but it doesn't have to be. 

Kitchens that have reached the end of thier life of 20 years may have wiring that has many more year left. Provided the electrics are in good condition and you are happy with the positions of switches and sockets, then you may not need to spend anything. 

If however you are doing a kitchen renovation because the kitchen was installed in the 70's and its time for a make over, then you may need to consider spending quite a sizable sum. 

For a more comprehensive answer on the cost of rewiring a kitchen, you can read my article The cost of Kitchen Electrics