E0007: a $ escape that a string literal does not have

In a string literal, $ starts an escape (Ed.3 Table 7): $$, $', $", $L or $N (line feed), $P (form feed), $R (carriage return), $T (tab), two hex digits in a STRING or four in a WSTRING, or a character code in braces, ${1F579} (Ed.4).

s := 'cost: 5$';      (* E0007: '$' at the end *)
s := 'cost: 5$$';     (* fixed: a dollar sign *)