Count me in as another person living happily on under $45K. At the moment (now that we moved to CA and our rent doubled) we're probably at about $35K, after-tax. (We save about 50% of gross income, pay about 25% in taxes, and live on about 25%).
I don't feel deprived at all. I feel that I have everything I want, or can get it if I really want to. I have found that people have a hard time with this concept (living well while not spending a ton of money) and actually that prompted me to write a book (currently looking for a publisher) and set up my web site for more musings on the topic .
I think you hit on the major points of not spending a ton of money. One thing you didn't mention was having only one (modest) car. My husband and I have always had only one car, and it's always been a small, inexpensive, PAID FOR car. We pay less in insurance in a YEAR than most people pay for one month's car payment. This has meant that we have to think a little bit about transportation options, but it has always been do-able, since we plan where we live accordingly. (Right now he bikes to work and I work from home, and can walk to do most errands, so the car doesn't get used much at all.)
I'm a good cook and that's a big factor in why we don't go out to eat more than a couple times a year. Why go to some place, have to wait around, and pay a bunch of money, when I can cook something as good or better at home? I'll note that it wasn't like I was born a chef or something. I learned in the good old trial-and-error way in college when I first got off the meal plan, and pasta with tomato sauce or brownies from a box were big productions.
In general, a big thing is just to not buy "stuff." I mean, people spend so much of their money on "stuff." New clothes, gadgets they never use, who knows what. If I buy something, it's because I genuinely want it or need it, and I'm going to use it until it wears out. Our spending on clothes averages $5-10 a year. (yes, a YEAR not a month). Clothes and shoes just don't wear out that quickly if you take care of them! (And I'm not some fashion maven who gets "tired" of stuff... if I liked it last year, I'll like it this year.)
And yeah, I don't give a damn what other people think (as someone else mentioned). "What would the neighbors think?"( or other permutations of that question) is utterly irrelevant to me. I occasionally get "Why don't you [buy X] - you can afford it!" from relatives, and they don't really get it when I say "I don't want to buy X, I'm happy with what I have." I mean, I could replace my admittedly rather shabby-looking coffee table, which I bought for $10 at a flea market 10 years ago.... but you know, I really don't want to. I LIKE that coffee table. It has exactly the features I like (drawers, two shelves) and it's just the right size. I can put my feet up on it and not feel like I'm messing it up. And it works just fine, even if the finish is worn. Not to mention that it has fun memories attached. Why would I want to get rid of it? If it eventually breaks, that's another story, but for the meantime, it's irrelevant that I can "afford" to buy an expensive fancy coffee table... I like my old one just fine.
Well, that was kind of a rambling example, but that's the kind of thinking that saves me a ton of money (and helps me be very contented with what I have, at the same time.)