Tom,
It is costing us more due to the size of the chipping areas not because of the style. Before the renovation we were walkmowing all of our chipping area. They have been significantly increased in size. I feel keeping a light mower on those edges are the key to keeping the edges. We mow these areas with a Flex 21 due to the amount of contours. We have heavy clay soils that have been modfied over time with heavy topdressng. One thing I am going to do differently is topdress these areas with a dirtier mix. Perhaps a 6-2-2 just to add a little of organic on these edges. Also keep in mind we are in Scranton, PA at 1600 feet of elevation. We don't see to many +85 degree days.