What would you do? #144 - Facing river pot bet with PP AA

Full Tilt Poker $0.25/$0.50 No Limit Hold'em - 9 players
The Official DeucesCracked.com Hand History Converter

MP2: $50.00 - 9 / 7 / 28% steal / 1.8% 3bet / 1.0 aggression factor / 133 hands
CO: $20.25
BTN: $54.55
SB: $34.75
BB: $35.20 - 44 / 6 / 0% steal / 0% 3bet / 1.6 aggression factor / 48 hands
UTG: $105.40
UTG+1: $51.20
UTG+2: $53.70
Hero (MP1): $74.55

Pre Flop: ($0.75) Hero is MP1 with As Ah
3 folds, Hero raises to $1.75, MP2 calls $1.75, 3 folds, BB calls $1.25
The BB coming along can only mean one thing: AK or PPs.

Flop: ($5.50) 8d 2h 4s (3 players)
BB checks, Hero requests TIME, Hero bets $2.75, MP2 calls $2.75, BB folds
Yuck MP2 flatting in position.  He's either got 99+ or a flopped set.

Turn: ($11.00) 9d (2 players)
Hero checks, MP2 bets $7.50, Hero calls $7.50
Modest-sized turn lead.  I'll peel one more & see if he slows down.

River: ($26.00) Jd (2 players)
Hero checks, MP2 bets $26, Hero requests TIME, Hero folds
I've got to be beat here, right?  He's not shown to be an aggressive player.  Easy fold?

I feel like I've seen this dance a million times before: build a pot, build a pot, build a pot.  A 9/7 is overcalling with two ranges: low pocket pairs and AK.  Is AK or a low pocket pair ever value betting with a pot sized bet on the river?  Is a low pocket pair flatting the flop?  There are no obvious draws for a 9/7.  This is a flopped set, where I think I paid $7.50 extra to find out.

Final Pot: $26.00
MP2 wins $24.70
(Rake: $1.30)