The proprietor of a fair ground does not mind running his swings at a loss if
his roundabouts bring him in a handsome profit. He can afford to provide
swings for the few people who enjoy them and who will very likely pay to go on
the roundabouts as well. Similarly a newsagent may make a much smaller profit
on newspapers good for trade because customers who call in for them will often
buy other things at the same time. Another aspect of the proverb is that
although the swings make less profit than the roundabouts today, they may make
more profit than roundabouts tomorrow.