The Covenant of Grace is a Costly Covenant

"The two covenants differ in this — the one was vastly more expensive than the other. The one cost the Almighty but the breath of his lips. He spake and it was done, he commanded, and it stood fast. But the other required vastly more. There was need of more than words to establish it. Who can fully declare what the covenant of grace has cost a Triune God, Father, Son and Holy Ghost? To accomplish its great ends,  

"God behoved to tear his Son as from his bosom, and to send him forth made of a woman, made under the law, Gal. iv. 4. To recover enemies, he behoved to part with an only Son. Ere he could smile on them, he was to frown on him and to desert him: before he could put the sword of justice as into its scabbard, he behoved, Father as he was, to plunge it into the bowels of his own, his only Son.  

"The Son, the Mediator and Surety of the covenant, behoved in virtue of his suretyship, to forego the ineffable pleasures of a Father's bosom, to be clothed in the likeness of sinful flesh, to be a reproach of men, covered with darkness, surrounded with sorrow, overwhelmed with fear, attacked by devils, stricken, smitten, and forsaken of God, and at last to die. What amazing cost is here! To use the words of one, " It is an expended Deity on human weal!"  

"The Holy Spirit whose it is to apply the Covenant to sinners, how costly work is it to him! He strives more with one sinner in a day, than ever he did with angels since they fell. He never knocked at their door, but, oh, how long he stands at that of mankind-sinners! How he strives and expostulates, ere he get access. What rebellion often against him! what resistance! and when received, what untender treatment often follows! Sons and daughters vex, grieve, and well nigh quench him. And thus as violence was done to the Son, so also to the Holy Spirit. He suffers in his influences and operations, though he cannot in his adorable person. He bears with the manners of his people, though often grievous to him, and does not altogether cast them off.  

"Thus the covenant of grace is a costly covenant. Nothing could be equally so. The salvation of one sinner has cost God more than creation in all its extent, pomp and splendour. Ten thousand worlds had been as easily created as one. But to accomplish the ends of the covenant, what did God do? I shall tell you in the language of inspiration, and if not inspired, perhaps it had not been safe to use it, " God laid down his life," 1 John iii. 16. And now, my brethren, what could have been done more for the vineyard than has been done? Isa. v. 4. Surely a synod of angels could not say. The cost could not possibly rise higher: God spared not his own Son, but delivered him up for us all: Awake, said he, O sword, against the man that is my fellow." 

Thomas Bell. A Treatise on the Covenants of Works and Grace, 213-214