On convenience of healthy food. It's very subjective for me since I was raised on organic food (farmerboy here, it is quite interesting that our farm was organic waay before "organic" even existed. Industrial farming just didn't seem "right" to my parents) I have a general distaste for any kind industrial food (except various sweets :D). Thus you will not find any sodas and/or McStyle food on my menu - because I just don't like the taste of it. (Yes I will turn into a BK or MD every now and then - just to find out that I don't like it - over and over :))
But - being a geek I also have (or at least had) this problem of seeing food preparation as too mundane for me. However since I quit my corporate job I actually started liking to take care of our garden (40m2 in backyard) and orchard, and I have always liked cooking (I love nice tasty food). So now I have learned to treat it as a stabilizing factor in my life, to just you know - slow down for a while while doing gardening tasks it also provides a basic exercise. I know understand that producing your own food is not an option for you - I'd just like to point out that eating a meal that you produced from ground up is one of best experiences in life - right there with drugs, sex and programming. Just to let you know that if you ever get a chance at producing your own food - you should take it. It's not too much work either. A couple of weeks in spring and one in autumn - in between its mostly about basic maintenance and pest control - nature takes care of the rest. Like mentioned - this last paragraph may not do much for you and you might even see me as (rightly) bragging - but it's here just so you can understand what angle I am coming from.
Now about how you can make healthy food convenient and cheap. 1. Accept that it will take more time than junk-food (thats half of its point), but it will take less time than you expect - especially once you get used to it. 2. Stop consuming sodas and just divert "soda fund" into "food fund" - you are meant to drink water and should learn to do it ASAP. 3. Beans, Pasta, Potatoes, Full corn Bread, vegetables, nuts and dairy products should be the staple of your diet. 4. A lot of home cooking can be done fast or semi-absent (vegetable soup - cut vegetables, add water, put on an appropriate power setting - return after an hour or two - enjoy delicious vegetable soup). Pasta is fast and simple to prepare (also will keep you well fed for quite awhile). To maximise yield, learn to cook larger amounts - don't just cook a single meal worth of soup or pasta. Example: Cook a pound worth of beans (this is 4 days worth of protein) - meal 1: eat some beans with cracklings; meal 2: use some of the beans in salad; meal 3: cook some bean soup with pasta; You can also use your vegetable soup as basis for your pasta sauce, etc. 5. Salads are super fast to prepare. 6. Fruit meals require no preparation.
But you could also view your food preparation as a ritual that will help you stay balanced in your life - and thus not a waste of time.
Oh and to be honest - its perfectly possible to grow fat on healthy food. It's just not so easy and your organism will not have to endure so much stress.