People don't dick around when they are buying houses,
I know some real-estate sales persons that would disagree with you. They see people making offers on houses WAY out of their price range and then the financing never comes through. Spend some time with an experienced agent and they'll have lots of tales of woe that sound exactly like the tales of woe from cars sales.
Me, I never give a deposit until a deal is struck. We're still negotiating, and the "credit card with offer" tactic is simply to get you to not walk out the door. It's to their advantage, so I don't do it. I do things that are to my advantage, not someone elses.
When I bought my house, my offer came with a $1 deposit. Sounds terrible! People will freak out. But, I had two other houses I was interested in and didn't want to get nailed down by having my deposit tied up. I made it clear that if we struck a deal, I would give a substantial deposit at that point, to give peace of mind for the seller, as there is always a time gap until closing.
committment to purchase TODAY
I never have to lie about that. I don't impulse shop a pair of $600 mountain boots, and I sure don't impulse shop a $20,000 or substantially more automobile purchase. I always say "no" to the "will you buy it today" question. It's a lot of money and I don't spend that kind of cash lightly. You might be in a rush to sell the car, but I'm not in a rush to buy it. In fact, I have never bought a car from someone that used that statement. It kills the deal for me. You're too desperate and I don't like desperation.