Some spells have expensive material components. In the case of restoration(s) it takes the form of 100-5,000gp worth of diamond dust, which seems to be a common spell casting material component. Now resurrection requires a diamond worth 10,000.
They both require diamond, just the form of it changes. Would it be acceptable to use diamond dust worth 10,000 since that should be much easier to acquire than a single diamond worth 10,000? Its also more versatile since you can just keep pouring diamond dust until you run out or have enough than having diamonds.