You can make decent money with a BA in Psychology. Many people end up as case managers, psych technicians and the like, which is a pretty good job to have. Of course you have the option of pursuing a career in many other fields — because often a BA is required, but not a specific one. You’d end up in a similar position if you were getting a BA in Biology, for example.
Anyway, it helps to know what you intend to switch your major to. If it’s Chemistry, I don’t think many of those courses would count beyond electives — which may or may not satisfy upper level electives you may need to take. However, if you were doing English, Sociology, Social Work, Anthropology, and stuff like that, it may satisfy core requirements for some, and maybe electives for the others.
ETA: Nowadays, a degree is a degree. You won’t be looking at amazingly high paying or specific jobs without a graduate degree. Whether it’s English, Psychology, Biology, Architecture, etc., you’re qualified to work as a manager, a tech of some sort, some random middle-of-the road job, or qualified to go to graduate school. Why change majors for the same outcome? Unless of course, it’s Computer Science or something — that gets you a pretty damn specific and good job.
I got a BA in psych, worked as a case manager, and then went to grad school. I’m going to become a counselor pretty soon — which not only pays very well, but is what I love to do.
My Future Sister-In-Law got a BA in Biology — and worked in a random office. With an MA now, she is a lab tech — and makes so-so money.
This has been the case for many people like us — so a BA really doesn’t seem to “count” unless it’s in one of the booming fields like CS or engineering. It doesn’t mean your degree is worthless, it’s just means you’ll have a non-major specific job.