With 4 children I'm told all the time by strangers that I "must be mad" or "blimey, you're brave"
I would think that as well
, but I only have one, so you can have my share.
I would aslo think of the expense. When they are little they can wear hand me downs and play with each others toys. Once they are teenagers they get very expensive - clothes, Christmas presents, bierthdays etc.
I expect that they will each need a laptop once they are at GCSE level and above. And the big one - university. Boy, that is expensive, even if all of your DC have jobs and can top up their maintenance loans.
Plus all the drudgery looking after a family of 7 - cooking, cleaning, washing up, washing and drying, running children to parties and after school activities, no "me time".
I'm judging you by my own values, but I need, and have a calm and ordered life, but that is just my personality type.