(business, stock market, chiefly northern US and Canada) Stock market securities can be expected to increase in value to a greater degree in the cold winter months from November through April than in the warm months from May through October, and profit-minded investors should manage their portfolios accordingly.

Inexpensive goods and services tend to be inferior to more expensive ones.

(humorous) Being available for sexual relationships with various people is preferable to committing oneself to a single partner.

Alternative form of why buy a book when you can join a library

Do not expect somebody to make a costly commitment if it will give them nothing they do not already have; used especially as a warning against having sexual intercourse before marriage.