A6&7, some way f helping a fellow member out
By the way, an Accord is not necessarily cheap, and a 3 series is most definitely not a sports car.
Del, That is absolutely not right. You are probably having to pay extra for synthetic and for the rarity (as far as they are concerned) of the filter. You should look around for a better deal. Ask RoadsterMadness and Teh Prof how much they get charged for oil changes and where they take their cars
Another option is to find someone who will change your oil if you provide the oil and filter. Then you are only talking about labor.
Five years ago, the oil change for my E36 was $125 at the dealership in BMW of Northwest Arkansas. I've heard up to $175 here in TX. My very first oil change on the E36 back in 2004 was the only one I paid for. I shamefully admit I took it to a Wal-Mart, and paid around $70.
Where did you have the oil changed for your 318i? [edit: just read you mention your E36]
Keep in mind that synthetic will last you a lot longer than the dyno oil in the Accord. I change my oil every 6k miles, but the dealership swears that it can last anywhere fromm 7.5k to 15k. If you change your oil every 10k miles, you're spending the same per mile than your GF is on the Accord (assuming oil changes every 3k miles). If you change your oil every $6k, you are spending an extra $5 per 1000 miles on your car than on the Honda.
An independent mechanic will probably charge you about the same: parts will be about $35, and you will probably get charged for one hour of labor at around $60 - $80. You can always try what I suggested above about providing the consumables.
It really is a shame that you won't do your own oil changes. The fact that I will do my own maintenance work was a big factor for me deciding whether to buy a BMW.
So, to answer your question, expect to pay from $75 - $200 for an oil change.