They won't always be on par, but if the gateways are doing their jobs, it should almost always be very close. Every failure is a profit opportunity.

Yes but no. A payment will take from offers if that's the best payment path. When making a Ripple payment, this is the typical payment mechanism:

1) The client gets the destination account and destination currency from some source. ("Pay Jeff 50 Bitcoins.")

2) The client looks at what the user holds and picks one or more source currencies to use.

3) The client asks the server what its options are. The server forms payment paths using the various possible source currencies taking into account what the destination will accept. These payment paths can ripple through accounts that hold and accept multiple IOUs but also offers. No transactions have been performed yet, so this is all free.

4) The client tells the user something like "You can make this payment for 50.03 bitcoins or 125 USD."

5) The user picks a source currency.

6) The client assembles one final transaction, incurring one fee. The transaction can include multiple paths (so long as they use the same source currency). The transaction can include a "maximum to spend" and the transaction will fail if it would cost more than that.

7) The client submits the transaction. The servers process it. The transaction is accepted. (The servers will take incrementally from more than one path of the paths explicitly specified in the transaction to get the best result.)

Notice that only one transaction is needed, even if you ripple through multiple accounts, take from multiple offers, and so on. The one and only transaction is basically "get Jeff 50 bitcoins he'll accept and don't charge me more than 50.03 Bitcoins to do it."

Possibly. But I don't see why that will be bad. Since there will be many possible paths for the same transaction, costs should typically be low. We'll see.