True about currency conversion. Apple could raise prices against other currency to make sure the value is equivalent to the USD... like against the Pound. However, most of the time when I have checked, Apple charges most international sales at a much higher price when the currency is converted to the USD. In the US, the prices stay constant.
The price for a MBP has been $1999 and $2499 for three years (I don't know before that). The price of low-end MB has been $999 for three years... other prices were $1299 and $1499. When changed to unibody MB (a complete redesign and not just speed bump), the prices were raised $100, but if you compare getting aluminum versus plastic, the reason is obvious. So, the low-end stayed the same at $999, and aluminum is now $1299 and $1599. However, I would say the low-end is the barrier to buy, and that has stayed the same. Especially if you base it on the plastic MB which has had its internal components substantially improved for the same $999.
The whole point I feel about the pricing, is that if you buy a new MB today for $1299, you are getting the exact same MB that you could have bought four-and-a-half months ago for $1299. So, it's always better to buy as close to the day after the release date with this pricing model.
The price of technology components USUALLY drops drastically especially over six months. So, pulling a random number out of my a$$, let's say it cost $700 for all of the components Apple uses to build at introduction. The cost may drop by $200+ over six months. So, Apple has to be making MORE AND MORE money until it updates the components again.
That means the buyer gets a better value by buying the MB as close to the release date (after not before) as possible. Look at the MacMini, the dang thing has to be nearly free for Apple to make now, but that wasn't the case when it was released. Also, look at how the sales have dropped in all of Apple's desktops. Let's say you're buying a Mac Pro, would you really drop $5k on a Mac Pro right now when you can get newer technology by waiting a few months until Apple updates it? It's the exact same thing with the MB only on a much smaller scale.
Plus, we have seen some new technologies introduced since the MB and 15" MBPs were introduced. Like the new battery in the 17" MBP, maybe Apple will add that technology to the MB??? It's possible. 8 GB RAM??? Ok, doubtful. Maybe Apple will re-add FireWire since the level of complaining was unbelievable - if it will ever happen again, it will be on its next release... So price alone is not the only reason to wait since it has already been 4.5 months since the last MB was released. For 15" MBP buyers, they definitely should consider waiting, as the battery is a definite possibility along with probably 8 GB RAM option, and perhaps most importantly for many an anti-glare display.
Waiting right now could pay off, or it could be a complete waste of time if the MBs and MBPs are not speed bump and BTO option updated soon or there are no changes other than minor speed bump updates. I definitely think Apple will update the 15" MBPs to have the same speed CPUs as the 17" model and likely have more BTO options like anti-glare, higher capacity SSD, and 8 GB RAM.