Mother in law will watch her grandson on Saturday for a price: Is this fair, strange, appalling to you?

My mother in law has watched our son on select days of the week while we pay my sister who also has a kid my nephew, and we pay my sister. My mother in law told my wife she would be able to watch our son on Saturdays for a cost (same rate as my sisters payment). The kicker is we save driving time which is good.

But am I wrong to feel weirded out that this isn’t free? I mean she watches him any other day for free. I find it strange while my wife is 100% ok with this.

What’s your take?

Some background. She watches him on Sundays for about 4 hours. Saturday will be for about 4 hours as well. I guess the strange part for me is she invited herself to watch her grandson but also asking for the money.

This isn’t the first weird financial related situation we’ve been in with her. My wife has a minor automobile accident and my wife pays her mother the insurance cost every month since they’re all on one plan (her sister, herself and her mother). When my wife wanted to pull out the money from the claims she wasn’t allowed to because her mother wouldn’t let her. Her mom had put the money from the auto accident into a fund where she previously borrowed from her own mothers death (my wifes grandma passéd away and money was split amongst her kids my mother in law being one of them) I guess she borrowed money from that pot and used the auto accident money to pay back the fund that was borrowed.

I don’t like the direction this is going in because if she passes away, I’m not sure if my wife will be able to attain those funds as it’s now in a pot that was split between my mother in laws sisters and brothers.

Anyways, how should I bring up my concerns in a way that doesn’t make me seem like a money hungry mongrel.

Should we just forget about those funds? Maybe paying my mother in law isn’t such a bad idea?

Thanks for the input.