Roger means it cost Jesus everything so you shouldn’t call it cheap. What Bonhoeffer meant by cheap grace is that it costs the believer nothing. The term is appropriate.
The bringing forth of grace cost Jesus everything, and having brought it forth, He gives freely to His chosen: its price is far beyond anyone's ability to purchase or deserve it-- that is what makes it grace -- if it has to be purchased, earned or kept by man in any sense, then it isn't grace.
That it is it is a completely free gift from God, is the secret that He has hidden away and shares only with those whom He saves after salvation: God is an exceedingly merciful, gracious and kind God far beyond anything that we can think or imagine.
I'm not at all hopeful that in asking this will do any good, but once again I'll try and humbly request that the following verses be studied slowly, repeatedly, carefully, and pondered deeply for their intent.
These verses are just a sampling of the verses that pertain to grace and salvation.
[Heb 7:25 KJV] 25 Wherefore he is able also to
save them to the uttermost that come unto God by him, seeing he ever
liveth to make intercession for them.
[Rom 1:5 KJV] 5
By whom we have received grace and apostleship,
for obedience to the faith among all nations, for his name:
[Rom 4:4 KJV] 4 Now to
him that worketh is the reward not reckoned of grace, but of debt.
[Rom 5:15 KJV] 15 But not as the offence, so also [is]
the free gift. For if through the offence of one many be dead,
much more the grace of God, and the gift by grace, [which is] by one man, Jesus Christ, hath abounded unto many.
[Rom 5:21 KJV] 21 That as sin hath reigned unto death, even so
might grace reign through righteousness unto eternal life by Jesus Christ our Lord.
[Rom 11:6 KJV] 6 And if
by grace, then [is it]
no more of works: otherwise grace is no more grace. But if [it be] of works, then is it no more grace: otherwise work is no more work.
[1Co 1:4 KJV] 4 I thank my God always on your behalf, for the
grace of God which is
given you by Jesus Christ;
[Gal 2:21 KJV] 21 I do not frustrate the
grace of God: for
if righteousness [come] by the law, then Christ is dead in vain.
[Eph 1:7 KJV] 7 In whom
we have redemption through his blood, the forgiveness of sins, according to the riches of his grace;
[Eph 2:5 KJV] 5 Even when
we were dead in sins, hath quickened us together with Christ, (
by grace ye are saved;)
[2Ti 1:9 KJV] 9 Who hath saved us, and called [us] with an holy calling,
not according to our works, but according to his own purpose and grace, which was given us in Christ Jesus before the world began,
[Tit 3:7 KJV] 7 That being
justified by his grace, we should be
made heirs according to the hope of eternal life.
[Heb 10:29 KJV] 29
Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath
counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done
despite unto the Spirit of grace?
[1Pe 1:10 KJV] 10
Of which salvation the prophets have enquired and searched diligently,
who prophesied of the grace [that should come] unto you: