If you are looking for a great little greenhouse at a good price, I’ve found one, but it’s only on sale until 
Sept. 15th, 2008. I’s on sale again! It’s under $300, and you can buy it here.
It’s a Juliana, leanto style greenhouse. When the sale is over it will be about $460. Even at that it is a good buy. Juliana is one of the Top greenhouse manufacturers in the US.
Generally, I don’t recommend any greenhouse kit below $400, but if you are just getting into gardening and you really want a cheap cheap greenhouse kit, there are some options. 
Generally, they are quite small and covered in plastic film, rather than rigid glazing. A good example is this 4′ by 6′ greenhouse kit for about $115. This little greenhouse kit will definitely get you started, if you aren’t serious about greenhouse gardening, but, as I said, I don’t generally recommend kits in this range.
Other inexpensive greenhouse kits are often difficult to put together. You really need to make sure you are buying a good brand. A friend of mine bought an inexpensive polycarbonate glazed greenhouse kit, and had nothing but complaints. First, it took forever to put together, then it had great big air leaks that he had to seal up. The good price was not worth the headache. And of course, if he had hired someone to put it together, or even help him, the labor would have more than eaten up the savings on the purchase price.
