This question is completely natural for any parent. It does not even matter if the parent is new to parenting or already has kids.
The first thing we need to say is that the price is not something constant. It is dynamic by nature. Every single year, most products become more expensive. Car seats for children are no exception. That means any exact data we provide here may be accurate here and now but will most like be very off at some point in the future.
Nevertheless, we are not trying to avoid answering the question.
A typical, very basic car seat booster would cost you least. A hundred dollars is relatively high a price. A backless booster is even cheaper.
Infant car seats are a little bit more expensive in general but some of them cost more than that. They might cost you above three hundred.
Convertible car seats can be even less expensive than infant car seats, depending on the manufacturer. You should expect prices between $50 and $250. As you can see, there is quite a variety. Even then, some of them could cost approximately $600.
All-in-ones are the most expensive car seats in general. This does not mean there are no cheaper variations but an all-stages car seat could cost approximately $250.