500 $ monthly for Amazon ads?

Hi folks,

I want to market my non-fiction books (psychology), but I work full-time and have limited time for posting on social media.

Plus, I think social media alone won’t help much, unless you already have a vast social network.

Do you think it’s worth spending 500 $ per month on Amazon ads? Of course, I don’t expect to become wealthy in a couple of months, but does it pay off in the long run?

Thanks in advance & wishing you a sunny Sunday.