Some say that since the foolish virgins went to 'buy' oil, therefore, oil could not refer to the Holy Spirit, since the Holy Spirit cannot be bought.

..............We know that the Holy Spirit cannot be purchased for money,

..............But the Spirit-filled life has a price. It has cost some their lives.

Jesus set the cost of true discipleship to include all that a man may have in this world:
" If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea, and his own life also, he cannot be my disciple.
And whosoever doth not bear his cross, and come after me, cannot be my disciple."
...............Luke 14:26,27