It's not so much that money buys happiness, it's that all lives cost money, and happy lives cost a certain amount, which you can't escape.
In
@Villanelle 's case, the happier life is costing more than the previous miserable life, but it's not necessarily the increased spending that made it less miserable. There are plenty of ways to be miserable while spending a fortune.
Happiness costs money, it just does, and yes, denying yourself the things you need in life in order to be happy will definitely make you miserable.
I am much more happy walking in running shoes than in bare feet, but I wouldn't say that buying shoes makes me happy, but I would say that protecting my bare feet from gravel and grass shards is a prerequisite for my being happy.
I need food to live, and food costs money. I could survive on unseasoned rice and beans, but I would get scurvy and eating would be joyless. Flavourful and nutritious food is also a prerequisite for my happiness. Flavour and nutrients cost a significant premium above what it costs just to not starve.
Survival comes at a cost, thriving comes at a larger cost, and happiness comes at an additional premium.
Still, that doesn't mean that spending more makes life better.
There are far more options for spending that won't make you happy than will. My running shoes cost about $150, but there are countless more expensive shoes out there that would hurt my feet and lower my happiness.
Fresh herbs are something I find absolutely worth spending on to make my food more enjoyable, but there are many more expensive made-from-frozen meals I could order at shitty chain restaurants that I would enjoy far less than my own from-scratch cooking.
It's not so much
@Villanelle that you went from a miserable non-spendy life to a joyful spendy life, it's that you went from a miserable life to a joyful life and needed to come to grips with the fact that your joyful life costs more than your previous miserable life did.
Now, part of your former miserable life may have been due to under spending, but it seems like it was miserable for a multifactorial range of reasons.
You aren't just happy because you are spending more. You are living a happier life and it happens to cost more.
As for the restaurants, do whatever floats your boat.
If you truly truly hate cooking, then you shouldn't have cooking as a major part of your life. Are there better options than paying an insane premium for restaurants, which are also notoriously bad for your health? Sure, and you can take your time, do your research and figure that out for yourself. I know A LOT of people who pay someone to batch cook for them each week.
Only you can decide what's right for you, what your happiness looks like, and what is worth spending on.
Part of living your best life is learning that spending doesn't necessarily make you happy, but also learning the flip side: that being happy does require you to spend.
The trick is learning the balance and being aware that that balance will always be changing.
Reflect carefully, be perpetually self critical, and in the end, own your choices.
...and be happy.