Just a little anecdotal info from my experience at the dealership regarding pricing.
Being in Canada, there really is no such thing as a cheap oil change (unless you do it yourself).
The dealership I use has the usual "lube oil and filter" special which runs about $45 with taxes and environmental fees tossed in. When you look at the breakdown of the costs for their special, the oil filter costs $6 (cartridge in my case).
However, should you bring your own oil to have them put in, the oil filter now costs $12. Jobbers rate vs parts counter rate.
They are still the ones doing the work, but because you brought your own oil, the parts cost goes up to offset the loss of $$$ from not using their bulk oil (that's my assumption).
That was what ticked me off and made me decide to do my own oil changes. Also bought the OEM filters from an internet vendor instead of the dealer. Same product for half the cost.