I’ve never heard about people paying for R.C.I.A., but some parishes do ask for a small amount of money for that sort of thing, that way they can make sure their materials are up-to-date (books, videos, et c.).
No one pays for a sacrament. It’s a sin, in fact, if the priest refuses to perform the sacrament without pay.
However, it is common for a parish to ask for a donation, or to “tip” the priest (sometimes called a “stole fee”) when he does that sort of thing (burials, weddings, et c.).
Donating some money to the parish for such a thing is encouraged (since they do need to pay for heating, utilities, and salaries for the priest, the secretaries, and some other staff), but it’s usually not required.
If there’s some sort of financial hardship that makes it impossible to pay, the pastor’s almost always willing to waive the donation.