50NL: Trips on scary board

[mikeyp]

Party Poker No-Limit Hold'em, $ BB (9 handed) FTR converter on zerodivide.cx

UTG+1 ($41.45)
MP1 ($50.70)
MP2 ($54.35)
Hero ($111.05)
CO ($10.55)
Button ($48.05)
SB ($80.07)
BB ($50)
UTG ($52.70)

Preflop: Hero is MP3 with 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/club.gif[/img]. SB posts a blind of $0.25.
<font color="#666666">3 folds</font>, Hero calls $0.50, <font color="#CC3333">CO raises to $2</font>, <font color="#666666">1 fold</font>, SB (poster) calls $1.75, <font color="#666666">1 fold</font>, Hero calls $1.50.

Flop: ($6.50) 9[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets $6</font>, SB calls $8.55, Hero calls $2.55.

Turn: ($23.60) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, Hero checks.

River: ($23.60) 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">SB bets $15</font>, Hero folds.

Final Pot: $38.60
<font color="#009B00">Main Pot: $23.60, won by SB.</font>
<font color="#009B00">Pot 2: $15, between UTG+1, CO and SB.</font> &gt; <font color="#FFFFFF">Pot won by SB ($15).</font>

Results in white below: <font color="#FFFFFF">
SB has Kc Jd (two pair, kings and jacks).
UTG+1 doesn't show.
CO has Ac Ah (one pair, aces).
Outcome: SB wins $38.60. </font>

The river bet really confused me. I would have called $5... but $15 seems a little high for me to call. I had a good hand but there was just too much that beat me to call that bet. Any thoughts?