Cameo shots are close up shots of a selected area of the visualisation. If you are paying for extra details that are associated with a KBB image, then why not just go the extra mile and add in some cameo shots?
With regards to clients in the kitchen / bathroom sector, this can be a crucial addition to a set of marketing shots. Offering a focused, zoomed in shot of features such as tiles, faucets, lighting fixtures etc can provide a clear image in marketing.
Having an overall room with a highlighted product in focus that is being promoted would improve the quality of the image. Cameo shots show more detail than a normal shot, and the level of detail in a cameo shot and added to the overall scene would certainly be worth the extra cost.