The Federal Champion at wally world is pretty cheap, just under $20 for 100 rounds. On-line is good if you look for sales with 'no freight' promotions & it's out of state so you don't pay sales tax, but that generally means buying 500+ rounds. The main complaint I have with Walmart is the ones here don't carry a large stock & when they are out of stock, may be a while before they get more in.
Winchester 9mm. 115 grain from SGAmmo. $20/100 rounds