Originally Posted by
rubiksoval
Bulk purchasing power.
It's the same reason why Walmart is cheaper on everything than your local mom and pop grocery store.
Except that reason doesn't hold as you progress upward in price on the various models.
Example
Emonda SL frameset $1700
Emonda SL5 (105) $2700
Emonda SL6 (Ultegra) $3300
$600 diff
You get.. an upgrade to Ultegra (on Merlin, cost diff between 105 and Ultegra groupset is $185)
Wheelset upgrade (the upgraded wheelset costs $370 retail). No idea if they even sell the lower tier wheelset (Affinity disc), but let's put $100 as value difference.
Upgraded handlebar ($50 value difference)
Upgraded alloy stem (supposedly another $50 value upgrade)
Overall I come up with $385 difference in parts. If buying power enabled better better pricing, then Trek should be able to price these two models eg. only $250 apart in price. Pretty much you can almost always find it would be better to buy a lower specced bike, remove and sell the stuff on it, and buy and install the same 'upgrades' yourself.