It's often more expensive in ads like that just because it lets men avoid the awkwardness of telling their doctor they need some. Which, IMO, is silly - those guys (and gals) have heard and seen it all.
Retail pharmacies are cheaper. I work for Walmart, and ours is between $13 and $15 a pill. When you ask him for it, be sure and ask for the highest dosage you can (100mg for Viagra) - the tablets are splittable, and are all the same price regardless of dosage.
I haven't taken it before, but the Cialis daily is my favorite drug for this, it's a low-dose one that you take every day so the little soldier is always ready when you are (ideally). Cialis lasts longer in the body, so the doses accumulate a bit over the course of a few days. We charge $130 something for a month's worth (30 tablets), but same thing here, the 2.5 and 5 mg are the same price per tablet. If you can, just get the 5mg and split them. 2 months of being ready to go for $130 seems like a bargain as compared to getting maybe 10 Viagra for the same price, and having to pop them when you need to.