The previous $50 price tag was probably a serious miscalculation (pun intended) by the folks at Wolfram Alpha, when they launched their iPhone app. Pricing is an art, not a science. However, for a limited time only (the remainder of the year) they have decided to put it on sale for $19.99.
There was an iPhone-friendly mobile website that has been taken down to avoid the “why buy the cow when the milk is free” problem. We’ll see if the $19.99 price tag is still too high.
But if you’re inclined to jump at this lower price point . . . act now, supplies are limited. No rainchecks.