Actually - Viagra was developed to relax and enlarge blood vessels to improve circulation to the heart - indeed, it was developed as a medication for heart disease.
It does not CAUSE arousal. What it does is facilitate an erection (through improved blood flow) when you ARE aroused. You will not get an erection with Viagra unless you are sexually aroused.
And yes - it does "enlarge" the penis, but the effects only last about 4-6 hours.
I found a source for only $2.50 a dose and we have been VERY happy with it.
It doesn't enlarge it permanently - just while it's "active" - you get an erection, it gets larger, etc.
Just remember guys - there IS such a thing as too much of a good thing.
My commercial site sells "penis enlargement products" but we haven't tried them and probably won't, so I can't recommend them. But if you want to take a look at them, PM me and I will send you a link.