FBA fees are almost always cheaper than anything you can do yourself (Walmart Fulfillment Services, WFS, is also looking pretty affordable). There are also 3PLs that sellers will use (e.g., Deliverr, RSL, Swan Logistics), but using them almost always costs more than FBA or WFS.

But, as the other posters have mentioned. It's unclear what the intention behind this question is and what you're aiming to accomplish. If you're not too familiar with the Amazon FBA ecosystem, something like this may give you an early introduction to information in a way that's digestible: redacted

In no way am I recommending JungleScout, but they're a well-established service provider in the space, so their content should be relatively reliable.

Agreed FBA is worth it for Prime. In my view Amazon effectively takes a full retailer margin, except they get you to manage your own products on the site. It is worth it because they give you instant access to a giant market. However you need to have the margin to support it. Some rough guide numbers are: FBA - 12%, Selling fees: 15%, Promotion (pay per click or other promos) : 10%, Decent agent (I recommend this) - 8%. All that adds to a full retailer margin. You can do it for less but may not scale.