I found this page
from last October which has a table that might be helpful if the information is still current. There seems to be two different plans: a monthly plan (pricing changes with and without direct deposit) and a pay-as-you-go plan.
So, according to it, if I'm paying as I go, it costs me $2 per transaction to use their card. If I have a monthly plan (which carries a $3.50 or $7.95/month fee), it only costs me $1 each time I use my card. It doesn't cost me to load direct deposit, but if I top it off with an electronic check, it costs me $3.50 if I add on less than $1000, and it costs me $6 if I load on more than $1000. ATM withdrawals are $2.50, and if I get over-the-counter cash, that's up to 3% of the transaction, with a $5 minimum.
In general, I don't think prepaid cards help you build credit at all.
I know a lot of employers have been trying to move away from physical paychecks to direct deposit/prepaid cards for at least the last 10, 15 years. Rather than eating all the fees that come with a prepaid debit card, is there anything keeping you from establishing an account (no fees, free checks, etc, etc, etc) at a local credit union or bank, getting your direct deposit funneled through that, picking up a credit card, run all your spending through it, and paying in full every month?