Rob:
You are definitely paying way too much - but then you wanted a 5 star hotel ...
FYI:
A 30 sq m (323 sq ft) apt costs between 7,000 and 15,000 baht per month ($230 - $500). I'm paying 8,500, plus about 1,000 for electricity, water, etc., for a really nice building (Chiangmai Riverside Condo next to the Holiday Inn).
I always give this advice when traveling: Book a nice hotel for 3 days. Spend the first day and a half recovering from jet-lag and then start looking for longer term accommodation. You might need to stay an extra day or two but this will save you a chunk of money. In my experience it is ALWAYS cheaper to book in person - if you can turn around, walk out to go elsewhere. Right now it is a renter's market. Vacancies are everywhere so it is very easy to find special deals.
You should expect that rental of a motorbike or scooter to cost $100 a month but once you move here and get your retirement visa you'll want to buy as $1000 will get you a very good used one or $1500 a new one and they last virtually forever.
Being over 50 allows you to apply for a retirement visa. With it you can stay inside Thailand - no need for visa runs. It is valid for a year but you must check in with immigration (near the CM airport) every 90 days. I just did my first 90 day report. It took me about 2 hours. I showed up at 2pm, got a ticket number, filled out one very easy form, handed my passport to the photo-copy business there and told the girl '90 day report'. She made all the needed copies (at 2 baht per page so it cost me 6 baht) and stapled them together. I signed them and waited for my number to come up (about 90 minutes). I handed them the photocopies, the form and my passport (no money). Within 15 minutes they called my name and handed me back my stamped passport.
FYI: Also getting the retirement visa took me about 4 hours. I needed my passport (proving my age), a bank book showing 800,000 baht (or more) in a Thai bank account for over 3 months (I opened an account at Bangkok Bank the day after I arrived and deposited a bit of money - then transferred 2,000,000 baht into it a week later. Then I put 820,000 into term deposit at 3.25% - I never expect to touch that again as I will use it to annually renew my retirement visa). I had to get a letter from the bank (500 baht) confirming the account balance and show my lease agreement (you must have an annual lease - although it can be almost expired - ie: you've already lived there 10 months...). Plus, again, handing my passport to the girl at the photocopy shop and saying 'Retirement Visa' then signing each copy. Same deal with getting a ticket number, waiting for it to come up (although I left for over an hour and came back before it was up), handing in a single form (just slightly harder than the 90 day form) and 1,900 baht. Waiting an hour or so afterwards before getting my name called and handed my stamped passport with the 1 year retirement visa. That's it, Very simple. Do it yourself - don't pay others to do it for you!
I guess the main 'trick' on the retirement visa is you must have 800,000+ baht in a Thai bank account for 3 months BEFORE you can apply. That means it is very tricky with respect to continuous stay. You'll need to be here for 3 full months (probably a little more) before you get your retirement visa and that might be hard to do. If you can spend a month in another country you'll have no problem but right now the visa runs and multiple entry permits are very iffy so getting 3 months + in is difficult. (I did 3 visa runs to Mae Sai getting 30 days upon entry plus 30 days more each run. I needed that 3rd run to have my bank account aged 3 months before applying for my retirement visa).
Anyway, good luck to you, eh!