Is the oil mentioned, below, oil for eating and cooking, or the kind taken out of the ground?

Revelation 6:6 And I heard a voice in the midst of the four beasts say, A measure of wheat for a penny, and three measures of barley for a penny; and see thou hurt not the oil and the wine.

Also, is not the, "measure of wheat for a penny, and three measures of barley for a penny", similar to what happened in Samaria?

II Kings 7:1 Then Elisha said, Hear ye the word of the LORD; Thus saith the LORD, To morrow about this time shall a measure of fine flour be sold for a shekel, and two measures of barley for a shekel, in the gate of Samaria.

  16 And the people went out, and spoiled the tents of the Syrians. So a measure of fine flour was sold for a shekel, and two measures of barley for a shekel, according to the word of the LORD.

  18 And it came to pass as the man of God had spoken to the king, saying, Two measures of barley for a shekel, and a measure of fine flour for a shekel, shall be to morrow about this time in the gate of Samaria:

Also, over the years, I have heard over and over again, that this passage cannot be understood, unless it is taught by one who learned ancient Greek.

They say this is the only way to know that it is speaking of a day's wages.

Is it not clear in the scriptures that I read and copy here?

Revelation 6:6 said, "A measure of wheat for a penny".

Is that not the same word used by Jesus in Matthew 20?

Matthew 20:2 And when he had agreed with the labourers for a penny a day, he sent them into his vineyard.

Jesus spoke of a penny a day for wages.

So if it is a penny for a measure of wheat, is that not a day's wages, comparing Revelation 6:6 with Matthew 20:2?