The most common and most likely answer to this crossword clue is the 13 letter word AFFORDABILITY
I've seen this crossword clue in The Daily Telegraph
A
F
F
O
R
D
A
B
I
L
I
T
Y
Buddy explains!

The straight part
We know that "Inexpensiveness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case inexpensiveness = affordability.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does AFFORDABILITY mean?
AFFORDABILITY noun- The extent to which something is affordable, as measured by its cost relative to the amount that the purchaser is able to pay.