I would expect the rollers might be a bit cheaper elsewhere but the belt and seals I get from the dealer. The seals add up in price but they run dryer than the aftermarket ones. I do not know if there is any difference on the tensioner, I happen to just had a tensioner failure on the DOHC engine in my Diamante wagon. Engine started a rumble at about 3500 revs. I drove it home gently and parked it till I can service it, I have no desire to loose a belt. Engine has 265K on it with about 30K on the belt, rollers and tensioner.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.