Here are the facts as I know them.
1. Vendors choose a single price tier (not a price) for each app.
2. RIM determines the amount to charge for the app in each market.
3. RIM provides vendors with a list showing the actual amount charged in each country for the app. A tier-1 app like my own sells for 1 pound in the UK, $.99 US$ in theUSA, $0,75 US$ in Columbia, and .75 Euros in Romania, etc., etc, etc (it almost seem random - each market has its own price)
4. No mere mortal knows how RIM arrives at a price. The calculus may or may not reflect exchange rates, VAT, bribes, graft, money grabs and miscellaneous charges. Who knows? Based on my observations in point #5 (below), I believe that RIM is calculating the price on some notion of "what-the-market-will-bear-in each-market". If they think that Brits are likely to pay a premium price, then they price the product accordingly in that market. (Sorry, I have no say in this matter). On the other hand, if they calculate that a more depressed market (like Columbia) needs to be enticed with a lower-that-average price, then they price the product lower. (Again, I have no say in the matter). I believe that they seek to obtain a world-wide average that is close to the nominal price (e.g. $0.99 US for a tier 1 app).
5. Vendors are paid 70% of whatever RIM gets from you. No deductions or bonuses are levied for any of the factors that RIM may or may not included in the pricing scheme. If you are charged 1.98 pounds, then I get 70% of 1.89 pounds (converted to US dollars at the current exchange rate). We get detailed reports. I have checked these reports and done some rough analysis. I have found that whatever RIM has done to the prices, on average, I earn very close to .$0.70 US for each purchase.