Mostly depends on the parent, and their friends and family. We have friends and family with kids so clothes, boosters, cribs, etc. get sent back and forth. You can also get a lot of perfectly good stuff second hand via Kijiji, facebook, etc. for free or for cheap.
If you insist on everything new, and your kid has to have lots of cute outfits that they'll wear once (but it will look so cute on your Insta) then you can pay a bunch. Kids can pretty much just wear bodysuits and pjs for their first year.
There are upfront costs include car seat, stroller, crib, each of which can be a few hundred dollars or much less (per above).
Your baby's feeding and pooping schedule will also make a big difference. If they have explosive shits and spit up all the time, you're either doing laundry constantly or buying extra clothes, cloths, etc. Our oldest pooped once a week. Checked with the dr, no issues, just Tuesday was pooping day. yay! But it saved a bunch on diapers.
Are you having three kids? Your vehicle is too small and you need a bigger one. Even with one kid, and you want to go somewhere for a night? You'll have one bag for you and your SO, then you'll have a pack and play, a booster seat, a diaper bag, clothes for the kid, a stroller, food, snacks, bottles, monitors, etc. Your trunk is full. Interestingly, one night vs a week and the packing is barely any different, just more diapers and a some more clothes for all of you.
The biggest thing you'll lose is time. They eat different things than you. They have a (frighteningly erratic) sleep schedule. You'll be up at random times at night. Then they'll have lessons (swimming, dance, gymnastics, whatever), or other things to do. Some of those are fine, some are boring, some are fun as a parent.
They'll need to be taken to school/daycare, so you have to work that in to your schedule. Also, daycare needs to be paid for. Our neighbours had 4 kids (in 6 years!), so one parent just stayed home and didn't work, because the daycare costs and time commitment didn't make sense financially or logistically.
They will have sick days and someone will need to watch them. You can't send them to daycare with the flu (or other highly transmittable virus), so you have to stay home. Do you have sick days from work? Not anymore, those are your child's sick days now.
Also, you will eat cold food because you'll be preparing theirs, or cutting it up, or getting ketchup, or cleaning up spills (so many spills). You'll eat fast, like an animal, because the kids need whatever. You'll eat with other adults and notice you've finished your meal before they've finished taking pictures of their plate...and people are staring at you because you accidentally ate the tablecloth in your haste.
Use community resources like libraries. You're not dropping them off, but you take them, and then you sit there like a zombie while they colour, or hit you with a book. Also, libraries have tons of stuff to borrow for free, more than just books. Unless they were defunded because the librarian didn't remove Huck Finn from the shelves.
All that said, kids are the best. They'll be little shits. They'll come up and hug you. They'll try to be sneaky and suck at it, then they'll do something so cleverly deceptive, you'll just appreciate it. They'll tell you they love you (never gets old). They'll tell you they hate you (funny after the first couple times). They'll get hurt and need to go to the hospital. They'll embarrass you and make you proud. They'll totally suck at things. They'll do things that amaze you. They'll make you shitty cards that you'll keep forever. They are the best.