Where do they get the money? I'll tell you..
Watchtowers & Awakes - never used to cost more than $.25 - but, if offered for free & you tell the householder "a small donation" - this leaves them in a quandry as to what to give - most will give you at least $1.00. Same with books - what used to be a couple of bucks - most "free donations - the householder wouldn't feel comfortable giving more than $5.00.
Also - wills and life insurance policies. When my father died, my mom donated a HUGE amount to her local congregation. It was ridiculous, as now she is pretty much penniless living off his social security.