There is a voluntary church tax paid by members of the Reformed Church in Europe. My grandma did not attend church in the last few decades of her life, and she did not pay this tax. My parents were forced by the local pastor to pay those taxes in order for her to get a religious funeral by the Reformed Church.

So you paid a mutually agreed price for a funeral. If you didn’t want their services you could have gone elsewhere.

The funeral was paid separately on top of the money the pastor coerced them to give to the church.

There is no agreement involved when you're told your mother wouldn't be buried with what you perceive as dignity, and you're manipulated while in a state of shock and grief to think that the voluntary payment you're making is mandatory.

What do you think grandma would've wanted? Would she be mad at the church and felt entitled to be buried through their service despite not having been involved with that church for 2 decades?

Would she have felt it was her children's duty to pay more than necessary to be buried a certain way? I'm not asking this rhetorically. I really am curious. We all want a dignified funeral for our loved ones, but did grandma make her wishes known?

I don't think she has made her wishes known. She was religious, just not a churchgoer.