Absolutely right on here. Dealerships make a better ROE selling those additional services plus incentives(kickbacks) they get from the finance cos versus what they get from selling the actual vehicle.
Just keep saying no.
Another tactic, going into the deal, say you can pay in full (a bluff) and get their lowest price. Once there, say you might be interested in financing depending on their credit terms. 9 times out of 10, they will knock some price off their previous "lowest" price if you finance versus paying in full. Why? The financial cos pay them on the back end.
If it's a high interest rate, then pay the loan off after 6 months in full (or use a Home Equity loan).
If they give you a low interest rate or zero % financing then all the better.
Of course, with the current inventories their postion is stronger but it's something to think about.