I's say around £200 nearly nine years ago. We live far from family and wanted to have friends who had helped us a lot in that first year over, plus many of them had very young children then too so it was a way to socialise. I made a huge pot of breast of chicken curry with rice and chutneys and poppadoms and stuff like cocktail sausages etc for tiny guests who did not like curry to nibble on. We had beer and wine and non alcoholic and some decorations in the kitchen. I baked Nigella's old fashioned chocolate cake and we made pots of fresh coffee etc after - it all adds up! But it was a really wonderful relaxed day and it was great to see all our friends there - I can still remember that day very clearly 9,5yrs later
Second birthday we did more or less the same except I cooked huge trays of lasagne, home made garlic bread and salad - then cake etc.
After that we only had parties for her own friends.
I don't regret having those parties one bit. And as it turned out we couldn't have any more children so it makes those memories even more special for us.