I'm looking to buy a Madone SLR 7 Disc (Ultegra di2 8070). But it is $1500 higher than the SLR 6 Disc (Ultegra mechanical) with everything spec'ed exactly the same.

The difference is the same when you go from Ultegra mechanical to Di2 in all their high end bikes with everything else spec'ed the same. That just sounds crazy to me since you can buy an entire Ultegra di2 groupset for less than $1700 and around $1400 on Ebay. Canyon only charges $600 premium when you go from mechanical Ultegra to di2.

Am I crazy or is Trek ripping their customers off on electronic groupsets?