It's not a bad deal at all. The Jag isn't the most hi-tech of the Martin bows, but being an '07 you wouldn't have any problems getting parts for it if ever they are needed. Most everything used except the riser is pretty much universal to most of their bows.
And just FYI, doing some rudimentary math, your buddy wouldn't get $450 for it anywhere because that's about all he spent to get everything new, depending on what arrows they are.