Let me underscore what the folks have said about the barrel very likely NOT being worn out.
First of all, it's hard to compare rifling depth with your eyeball. If one bore is shinier than the other they will look different, for example.
Second, the rifling is not the same depth on all models. If you have a NEW P89 barrel for comparison then you can try to make a determination as to whether the rifling is more shallow in the used gun (comparing apples to apples) although it would still be difficult. On the other hand, trying to compare it to a different model is not productive at all.
Also, a worn out barrel will LOOK like a worn out barrel, not like a barrel where the rifling is just a little shallower. It takes a LOT of shooting to wear out a barrel. More to the point the gun will also look HEAVILY used.
Furthermore, EVEN if the rifling is shallow, the barrel is not worn out unless accuracy or velocity has dropped off to an unacceptable level. Even VERY shallow rifling is capable of spinning the bullet enough to stabilize it. Problems only develop when the rifling has worn so badly that it no longer engages the bullet or when there's too much gas blowby in the bore.
If you WANT another gun then go for it. But it is, in my opinion, HIGHLY unlikely that you really have a worn out barrel.