If you're up against a medium pair, it doesn't make much difference which way you go. You can keep your $260, or expect to win 45% of $600, which is $270. So the all-in move makes you $10.

It seems your fold equity here is pretty low. So the real question is, how often do you dominate compared to how often you are dominated by KK or crushed by AA?

I made a chart here, but it's not all that useful since I basically pulled the likelyhood of the hands out of my butt. My butt says call. Please adjust using your own butt.
<font class="small">Code:</font><hr /><pre>
Hand Likely? Win% win$ net EV weightedEV
sm.Pair 80% 45% 270 10 8.00
AA 3% 7% 44.4 -215.6 -6.46
Ax 8% 70% 420 160 12.80
KK 3% 30% 180 -80 -2.40
AK 5% 50% 300 40 2.00
bs 1% 60% 360 100 1.00
100% $14.93
</pre><hr />
captZEEbo makes a good point regarding your position. If it looks to your opponent like you might be stealing, your chances are a lot better.