Well then, There are a TON of free models on the net in EVERY genre imaginable.
I googled "free paper models architecture" and came up with many different sites that have such. Why pay for something that you can get for free?
I did the same thing with "Astronomical paper models" and got a TON of links.
Just make Google your friend and you will find more models for free in every genre then you can build in your life time.