As you can already see, every situation is different. For a number of reasons, employers offer different "compensation packages" regardless of career field. For example, some places offer a uniform allowance to buy scrubs while others feel the cost of uniforms is expected and rolled into your salary. My wife's employer pays for CEUs, but not memberships or license renewals. My brother (a mechanic) even had a job where he had to supply his own tools at his expense.
While I'd love it if my employer picked up these costs, the fact is that these are MY credentials and I made the decision to get them and need to maintain them. They normally buy one set of code books for the office but asked if I wanted my own set ... I declined and purchased them myself. Partially because I feel it's part of my professional expenses and partially because I want to feel free to tab them, mark them up, and take them with me should I ever leave. I also purchased a subscription to AAPC Coder when it was on sale to give it a try.
That said, if you have to pay for everything:
-Membership ($160/yr)
-CEUs: For one credential, you need 36 CEUs every 2 years. You can get 24 of those for free from the magazine. That means you need to find/purchase 12 CEUs over 2 years. There are free quarterly CEUs, CEUs through products like AAPC Coder or SuperCoder, CEUs for attending local meetings, etc. AAPC offers a Webinar subscription and have recently started offering a bundle deal when you renew. ($100-$200/yr depending on what you choose)
-Books: If you want/need your own books, or just don't want to share! ($200/yr)
-Everything else (optional): Maybe there's a conference, seminar or workshop that just interests you. Maybe you want to pony up the cash for AAPC Coder just to make your job easier. ($????)
That puts everything at around $560/yr or roughly $50 per month (which is what I budget). When comparing job offers you need to consider the "entire package" ... one employer may offer to pay for all these things (value: $560)... another employer's offer might be for 50 cents an hour more but not offer any of these things (value: $1040). Even after other factors like income tax, the job for 50 cents an hour more is a better deal than the one that offers all these "perks." I've seen people leave our office for "better pay" and not take into account differences in health insurance costs or 401k matching or whatever.
I know everything on the AAPC site looks entirely too expensive (my initial reaction), but almost everything goes on sale at some point - I purchased PractiCode for $50 (normally $300), AAPC Coder for $50 (normally $400), E/M training (10 CEUs) for $99 (normally $300), a few workshops for for $50 off, etc. You can find deals and will likely spend more each year on gas driving to/from work that you will pay to maintain your credentials.
Hope at least some of that helps!