I don't know how you can say that. The pro models have;
1) Faster CPUs
2) Backlit keyboards
3) Larger and higher resolution displays
4) Much faster and more powerful discrete GPU
5) More connectivity and can mirror or drive 30" ACDs
6) Larger and faster HDD options
and probably a few other things as well.
Just because they will supposedly be using Aluminum cases for both does not make the MBP any less superior to the MB. Function-wise the MBP is far superior. Fashion-wise they are equivalent.
1) By 100-200Mhz. Worth? $100 tops
2) That's a big deal? Worth? $25
3) Worth? $200-$300, based on industry prices.
4) They're only midrange, and
always outdated. Worth? $150 tops.
5) Great for some power-work users, but for the average consumer, worth little. Such features are crippled on the MB anyway and cost Apple very little. Worth? $50 tops
6) That also cost a ton more than they're worth above and beyond the retail prices. Worth? $100
Max total? $725 (and that's very generous, mind you. Just look around).
To sum up? For a 17" MBP over a top-end MB, I am paying $2800 vs. $1300, or an additional $1500 for $725-worth of features. And that's ignoring the fact that the Macbook costs twice the cost of competitors for similar features.
The MBP isn't much different than the MBP. But you're paying incredible prices for those differences. The MBP doesn't even deserve to be called "Pro". You can get similar specs for $1300 of your standard HP or Dell, with the same parts.