[RPG] Are normal spell components consumed by the spell

According to lead rules designer Jeremy Crawford:

The intent is that the shield hand can be used for a somatic component if the holy shield is used to cast the spell.

In a tweet exchange on 21-23 November 2014, @Sword_of_Spirit asked:

@JeremyECrawford Holy symbol engraved shield counts as material component, but does holding the shield replace somatic component also?

Crawford replied:

@Sword_of_Spirit The intent is that the shield hand can be used for a somatic component if the holy shield is used to cast the spell.

And further clarified that the shield arm cannot be restrained:

@Sword_of_Spirit You still need use of the shield arm to move it while performing the somatic component.

This is interpreted as (100gp worth of Holy Water) or failing that (100gp worth of powdered silver and iron) either of which the spell consumes.

Here is why.

A vial of Holy Water costs 25gp per vial. You will find on page 152 of the PHB that Clerics and Paladin exclusively are able to conduct a non spell ritual using 25gp worth of powdered silver to create Holy Water from scratch.

This 'equal exchange' potential is reflected in the material components for Magic Circle and I believe one other spell I remember coming upon. In this instance you need a cleric or paladin to turn 25gp worth of an item into 25gp worth of a different item.

In the instance of Magic Circle you dont need a Paladin or Cleric (though Magic Circle are class spells for them), you need 100gp worth of Holy Water or 100gp worth of its base materials that create holy water; Powdered Silver (plus Iron because in most cultures Iron helps bind those tricky creature types that magic circle is so effective against), in the absence of Holy Water.

Churches, temples, and shops that stock holy water are not always available in a campaign setting. Or maybe you dont have 100gp to buy all that holy water. Asking the local smith to grind up some iron and a few silver bits though? Pretty simple in almost any campaign.

It is also important to note that nowhere in the current full range of 5th Edition spells (PHB, EE, SCAG) are there any 'mixing' of possible component cost options. Only ever equivelant exchange. If the spell must consume one thing, it always also consumes your other option which is always of equal value to the spell. You will never have a choice between a cheaper consumed material cost.