They dont have a 30 as far as I know. They exist but arent that common. A 29g would be $29 plus tax and any equipment and decor you need for it.
This sale is great for people who have stuff lying around to set up another tank, but it really gets people that are itching with MTS (multiple tank syndrome) into the store buying gravel, fish, filter, heaters, decor, plants, lighting, stands, and all that stuff.
When you add it all up a 29g with equipment not counting a hood, lighting, gravel, fish, or decor (so just tank, heater, filter) would cost around $30 for the tank, $25-$50 for a filter (brand depending) and around $30 for the filter. So it is really about $85-$110 before you buy a hood , lighting, fish, decor, and gravel. All in a sudden a starter kit doesnt look too bad since it has the hood and light, but probably has a cheap filter and heater (if it even has a filter).