When the holy prophet (pbuh) said that such and such deed will give you that much sawab, I believe it is meant to show importance of that particular deed.
surely, Allah will reward us for the deed but we must also try to understand why this particular deed has been given this much importance. As far as surah-e-Ikhlas is concerned, it purely about tauheed and clearly states that Allah is one and only, no associates, no son etc. and of course tauheed is the corner stone of
our religion Islam. similarly, cleanliness is said to be half of the faith. this shows the importance of cleanliness as per Islamic standards. it doesn’t mean that one can be lax on other aspects of the faith.