Since 1990 in the US and since 2000 in the rest of the world, JWs have not had to pay upfront for the publications. Before that they did and then try and recoup from whatever talked people at the door into buying.
For example 25 cents per magazine paid by the JW
Offers to non-JW for 25 cents
No profit to JW, only breaks even but if the JW
Buys 2 magazines at 50 cents
places none, JW is 50 Cents in the whole but the WT organization has their 50 cents
Now the JW puts money anonymously into the worldwide contribution box at the kingdom hall.
Does not ask directly for money for the publications but does ask person at the door to donate to the "worldwide work."
Many JWs never put any money in the contribution box; and many never ask the non-JW to donate to the worldwide work.
Do you see that before 1990, the WTS had a steady flow of cash.
As to contributions to the congregation and to the headquarters, there are separate boxes. No JW is required to donate to either and it is anonymous (except if you put in a check; then the accounts servant who handles the money knows).
You don't have to donate to become a baptized member but if you want to get "priveleges" you give the circuit overseer and district overseer, traveling representatives of headquarters, a little green and suddenly you may find yourself giving talks at the conventions.
Every year in the WT (usually November issue), there is a detailed article how to donate to the WTS and how it is a tax break for you. Many congregations "bank" any surplus monies with the headquarters but some have found it hard to get it back. Also, the local administrators at the conventions manipulate the donations by making it seem they are in the whole to get the local JWs to cough up more money, $5,000 is sent then to the headquarters.
It is all behind the scenes.