In her Prologue the Wife of Bath claims to love sex more than almost anything else, but she just might care more about wealth. She admits to withholding her sexual favors from her husbands until they yield "raunsom," by which she means give her material goods. Her willingness to forgo sex for wealth probably results from her philosophy that everything (and she does mean everything) is for sale. Her philosophy seems to have paid off; we get the impression that the Wife has a good deal of property and a comfortable life.
However, despite the Wife's desire to accumulate wealth, she does break with her habit of marrying for money with her fifth husband, a poor student. He was good in bed, says the Wife, and besides that, she loved him. It seems that some things, money can't buy. On the other hand, it's thanks to the property the Wife has gained from her first four marriages that she's able to marry for love. This detail reveals the reason wealth may be so important to the Wife: it enables her to buy the thing she desires most, which is the freedom to do (and love) as she chooses.
The Wife of Bath uses the medieval equation of women with property to her advantage in her relationships by in effect trading herself for money.
Jankyn's lack of wealth means that the Wife's normal methods of gaining power in her relationships are ineffective with him; instead of gaining control of his property, she must gain control of his sympathy.