Even if the majority of rides come cheaper, that's still an insane pricing level. I suspect they've done their analysis, and found that the majority of people that buy these sorts of things, are people that buy all the extra content for "The Sims". No matter how cheap they make the add ons, I'm not going to buy one, and nor will most consumers, so they've gone for the customers that don't have any concept of value for money, and are instead obsessed with having "things" (ok, I'll take the risk and say it... Housewives). These people are limited in both number and intelligence, so they need to maximise revenue from this base, at the cost of all other customer bases. Hence the absurd price.
It's probably very good business sense, and comes from some quite careful and for once useful marketting study. Shame for gamers though.