Hello! Please have a look on http://www.osm.org/node/10766873019 (one of hundert and five objects). 
ee = 15 minutes @ 11000 JPY;20 minutes @ 16000 JPY;30 minutes @ 21000 JPY;45 minutes @ 31000 JPY;60 minutes @ 41000 JPY;90 minutes @ 15000 JPY;120 minutes @ 28000 JPY
fee:extra = 15 minutes @ 11000 JPY
Why did you need a key fee:extra? This value is part of the value of key fee also.