To clarify,,,,to use PBS postage service, coming out of my account will be 55 cents along with the cost of the Media Mail charge?

Yes, the 55 cents is the fee paid to Endicia, the online postage provider. As a Standard Member you will get one free printable postage a month if you want to try it out.

Personally I use Pirate Ship for any shipments after I use up the free postage credit I get each month. That 55 cents covers credit insurance as well, so it can be worth it for some.

To be clear, Standard members get one fee-free postage printing per month. You still pay the postage, just not the 55-cent fee. (The site pays Encicia's fee for you.) Limited members get one fee-free postage printer per quarter.

The .55 is worth it to be able to avoid going to the post office.  I just stick in my mailbox.