It depends where you're having it along with whether you are self catering or not and if you make you're own cake, buy premade or go to a bakery as that will change the cost. I'd say anywhere between £50 to £200 (you could easily spend more depending on venue)
Honestly, with our son’s first birthday, we weren’t quite sure what to expect and/or how to plan it. We just did a potluck style and just provided cake and desserts.
We spent around 3k 😮💨
We did it at home, and on decorations and food/drink we spent around £600.
We hosted around that many at our house and did pulled pork, potatoes, salad, chips and dips etc. Including ingredients, some nice champagne for a toast, a cake from Tescos for everyone else and a homemade baby friendly cake, spent around £60 I reckon? Certainly no more than £75.
We did an Alice in One-derland theme so it was tea party themed. We did 3 different types of sandwiches. The ingredients for cold cuts, tuna and egg salad came to about $35. I made the cake which cost me like $8 but a slab cake is usually about $25. I made all my decorations and went all out so I spent a lot but j could've gotten a decoration pack and they are about $30. So I'd say probably around $100. It will be more if you do pizza. Sandwiches were so cheap. That's Canadian prices. Probably cheaper in the States or elsewhere