Sorry, i don't understand why you would both go off and buy stuff without telling each other. Its not about getting permission, but respecting each other enough to value their opinions.
DP is quite good at coming home with a sheepish grin on his face having purchased some monsterously expensive tool for work. He hasn't done that lately as we have been strapped for cash, but he would never deliberately hide his purchases - i'll only find out at the end of the year when i do his accounts anyway , but he will buy stuff for work without boring telling me about it. Personal purchases we make together so its always spoken about, never deliberately hidden.
If money is tight, and you don't need the pram you are being unreasonable. These things have a way of biting you in the bum, because if, for some reason you don't pay up by the end of the terms, they usually whack a stupidly high interset rate on things.
We have fallen into the credit trap, but i can promise you that now, if we can't afford it, we wait, it has been a very harsh lesson to learn too, i promise you that.
Ebay is full of lovely second hand prams, i wish i had bought one, but my mother brought mine - i rather wish i had saved her money as i am quite reticent to give retailers my money these days, prefer to shop in charity shop, or should i say i am obsessed with charity shops