I don't think that's there's anything wrong with having an occasional lamb chop when the kids have pizza either.
Sometimes I might give the kids a pizza on a Saturday night, then later DH & I will have a chinese takeaway, or have a M&S dine in for £10. They don't like chinese, they do like pizza. It's nice to chill in the evening together with a nice meal and a glass of wine once they've gone to bed.
I don't feed them cheap stuff all the time. 99.9999% of the time we all eat exactly the same thing. I might adapt something we're eating to suit their tastes (and it may be that the substitution is cheaper) but it's not a regular thing. I'm not running a cafe cooking lots of different meals.
Sometimes they might have something cheap and quick (beans on toast/jacket spud) because they have to be somewhere else and I just need something quick and filling to shove down their throats before dropping them at a party or scouts or something, then DH & I will have a meal later
If we're out, they choose off the menu, it's usually cheaper as it's a children's portion (most places we eat serve the same meals on the main menu, just smaller, so cheaper - they can't eat a full adult sized portion), sometimes they like more expensive stuff, sometimes they like the cheaper stuff (DD1 likes mussels, but sometimes she wants the £3.95 chicken nugget & chips meal).
Yes, I do treat myself to the occasional bottle of wine or expensive box of chocolates, but we have a tuck cupboard which has lots of bits and pieces in they do like. They also get icecreams if we're out, popcorn, etc, etc, which I don't usually buy for myself.
My clothes are more expensive than theirs, theirs are childrens sizes, mine are adults, they are more expensive, but then they're more likely to get treated to the £5 t-shirt they like than I am likely to buy myself clothes.
Their rooms are smaller, but I share with DH and we have a double bed, 2 chests of drawers, 2 wardrobes. Their rooms are smaller, but there's less stuff in them and they have more free space than we do
They do activities, taxi-ed around to friends houses, taken to parties, cinema, bowling, I don't go to build sandcastles on the beach for my benefit. I don't regularly spend £2 a week on Moshi Monsters
It all evens itself out in the end