Online isn't going to be very cheap because of shipping. A 40 breeder is actually 47 gallons, given the width the $100 one you found isn't such a bad deal.
I've treated huge tanks for ich before. Just use 2 tbs/5 gal salt and turned the heat up to 87 degrees. And don't touch it except for water changes (add make up salt) for 2 solid weeks. It'll work, trust me. Get the pickling salt in the green box at WalMart for $1.12. I promise you-it WILL work. Just don't quit too soon.
Edit: A 125 gal tank takes exactly 3 cups salt at that dose, a 150 g takes 4 cups and a 100 gal takes 2 1/2 cups.
Thanks guys, found better deal at The Pet Place, and Petsmart matched the price.. to their kit! So I got the tank, cheapo light and the glass top all for $67 plus tax.