For the povo pack whiners who claim wearing Vaporflys is cheating - they actually provide 4.5% benefit. In the study, 50 g was added to each shoe to make it equivalent mass to the Adidas competitor garbage.
So unless you run with 50 g of pellets in your shoes, average benefit in running economy should be 4.5% assuming 1% increased efficiency per 100g mass.
Enjoy being poor and slow.