File format for highest-quality music downloads?

Audio quality is a top priority for me, so when I buy music I usually get a CD and import it into iTunes using Apple Lossless Encoder.

I'm now interested in an album that is not available on CD. My options to buy it are (a) via iTunes, or (b) on Amazon as mp3.

On iTunes, the individual songs are marked as being $0.99 each. Am I right in thinking that this indicates these are not the highest-quality files (if they were, wouldn't the per-song price be $1.29 each)?

Is there a clear answer on which format (standard iTunes vs. mp3) would be higher-quality? Or does it depend on the compression settings when the songs are encoded? Would I be best off listening to the samples on each site and forming my own conclusions about which sounds crisper?