can ill afford

The Art of ChoosingのLord of the Thingsの章に入りました。
Enrollment rate were dismal for those who most needed Part D--the low-income individuals eligible for full prescription drug coverage at no personal cost. If they enroll now, they will incur late penalties they can ill afford; if they don't, many will have to forgo medication that they can't pay for on their own.
"can ill afford" の意味は "cannot afford" とほぼ同じ意味だと思いますが、助動 詞の "can" と動詞の間に副詞が入っている表現は珍しいので辞書で確認します。
・Cambridge English Dictionary: (formal or old-fashioned): If you can ill afford to do something, it will cause problems for you if you do it: We can ill afford to lose another member of staff.
・Cambridge Advanced Learner's Dictionary: (formal can ill afford) If you cannot afford to do something, you must not do it because it would cause serious problems for you: We can't afford to make any mistakes at this stage in the project.: He can ill afford to fail any of his exams.
・Oxford English Dictionary: Only with difficulty; hardly: she could ill afford the cost of new curtains
"formal" って日本語では文語表現のことでしょうか。ところで動詞の "afford" は昔高校生の頃に "I can't afford a Ford." で覚えた記憶があります。未だにフォードは買えません。