There's a nice middle ground between new and old. As you might know already, huge depreciation happens almost as soon as you drive off the lot! Look for something that's just a year or two old, with less than your 55K miles, and reap the rewards. For $15K instead of $20K, you shouldn't have any trouble finding something that makes you feel comfortable.
If you're feeling more badass, though, here was my thought process as I look at replacing my 2002 Civic with 300K kms this year. I'm stuck commuting and put about 30K kms on my car each year. At first, I thought new was worth considering: nice, super fuel efficient, maybe even electric! But then I did some basic math. If the average quality car can go about 300K kms in its reliable life (my civic had very few repairs in it's life so far; tires, brakes, oil, wipers; at 150K did the timing belt, water pump. The AC needed a little work), and I drive 30K a year, then a new car is going to last me 10 yrs. At $20K minimum, that's $2000/year.
I can get another Civic in good shape with 100K kms on it for about $10,000 around here. Then I can put another 200K kms on it over about 6.5 years, or about $1500/year. For $5000, I can get a Civic with 150K kms = 5 years or $1000/year. I finally decided, to my surprise, that it's worth picking up a Civic with around 200K kms on it for about $2500, even though it means replacing my car every 3-4 years, which is undeniably a hassle. But I figure I'm doing my best to use up available inventory (so it's eco-friendly ish!). But my goal is to spend as little as possible on my shameful commute, so $500/year amortized purchase price works for me. In my experience, maintenance costs should be pretty consistent, and the bonus of more than 200K kms means many routine things like the timing belt change should already be done.
The point isn't that you have to go rock bottom like me, but that you can choose your price point and value consciously, factoring in the variables that you choose.