The cheap oil changes are 100% bait to get you in there. Sure there may be a few dealers here n there that don't try to up sell, but they certainly do up charge for anything beyond the basic oil change.
I don't frequent dealers. The POS dealer we bought our new SRT from wouldn't even cough up a farking t shirt,hat or free oil change, but he sure tried to sell me 5 different warranties like 10 times before we got him on track to do the title and registration!
Took my company truck to the Chebbie dealer for a complete service. Oil, trans, t case and axles. Oil change was like $65, great deal. The rest was like $700 before the $100 off "you spent too much" discount! Eash axle and t case was about $100 ea for a drain and fill of a couple quarts each and the trans was $300.