Many fitness centers are expensive to join or take classes from. You can often join for less through another organization. E.g., health insurance companies, employers, and some other organizations. E.g., see
SilverSneakers (on some Medicare supplement or advantage plans)
Silver&Fit (on some Medicare supplement or advantage plans)
Active&Fit (on some insurance plans, and other organizations)
(If you know of any others - please list.)
It is sometimes cheaper to sign up for the insurance than to join privately. I plan to pick my next health insurance plan based partly on that.
With some, you can go to any of the facilities they cover at different times - it's like joining many gyms.
BTW, I think most private fitness centers negotiate on price if you push - or they have discounted plans they don't tell you about unless you appear uninterested after hearing the initial price. Some facilities have major discounts for low income people and/or seniors. Some governments let low income people and/or seniors join government subsidized facilities and classes at a discount.
Many colleges and universities have highly discounted class prices for senior citizens. (BTW some professors let seniors do informal audits for free.) Sometimes that gives you access to their recreational facilities, which often aren't busy in early mornings, and/or to their libraries.
There are also cheap gyms, which I have listed
here.