But one halfpennyworth of bread to this intolerable deal of sack!

From Gaudy Night by Dorothy L. Sayers.  Page 224.

“Harriet said nothing, but continued to make out the cheques.

“One thing, there doesn’t seem to be much at Blackwell’s. A mere trifle of six pounds twelve.”

“One halfpennyworth of bread to this intolerable deal of sack.”

Harriet Vane is helping a student get his finances in order, primarily by discovering the expenses owed.  There are many cheques to be written for gambling, dining, and libatious indulgences.  

Having been to Oxford a number of times in my boarding school days, I know of Blackwells.  The counterpart in Cambridge was Heffers.  Both are major bookstores service the academic community of their respective universities.  Or what a heaven each are for a bibliophile.  So the student's expenses for books are a trifle to the expenses for inebriating pastimes.  

“One halfpennyworth of bread to this intolerable deal of sack" is almost certainly Shakespeare again, probably something to do with Falstaff, so Henry IV?  An artful critique of the student's spending priorities by Vane.

OK.  It is Prince Henry speaking about Falstaff in Henry IV.  And the scene is a close match to the circumstances of the student.  In this instance, Falstaff is suspected of a crime.  Peto is Prince Henry friend.  

PRINCE HENRY

This oily rascal is known as well as Paul’s. Go call him forth.

PETO

Falstaff!— [pulls back the arras] Fast asleep behind the arras, and snorting like a horse.

PRINCE HENRY

Hark, how hard he fetches breath. Search his pockets.

PETO searcheth his pockets, and findeth certain papers

What hast thou found?

PETO

Nothing but papers, my lord.

PRINCE HENRY

Let’s see what they be. Read them.

PETO

(reads) Item, a capon, … 2s. 2d.

Item, sauce, … 4d.

Item, sack, two gallons, … 5s. 8d.

Item, anchovies and sack after supper, , , , 2s. 6d.

Item, bread, ob. [halfpenny]

PRINCE HENRY

O monstrous! But one halfpennyworth of bread to this intolerable deal of sack!