Being honest with myself and taking input from my RAH I admit I have a tendency to make a sarcastic remark. Now that my RAH has indicated to me that it bothers him, I am trying to be aware and work on it.
Mostly for me the sarcasm comes when I am frustrated and can't express what my wants or needs are in a calm, clear way. I am not justifying this but just wanted to help you consider how you might respond to your AH.
For example when he made fun of your question about negotiating you might consider saying - 'If you have a problem with me asking a question or wanting to introduce negotiations into our dealings with the salesperson you can let me know ... I will not allow you to make fun of me and if you do so again or continue to do so we will have to discontinue the discussion until a later time.'
Not sure if this makes sense but I notice that when I express sarcasm my RAH is less responsive to me which makes me reconsider how I am speaking to him and what it is that is really bothering me that is making me choose sarcasm. Of course, I consider myself a considerate person and I am trying to work on this to be more compassionate to my RAH and to be a better person. Nevertheless, you sticking up for yourself and not accepting sarcasm may help your AH reconsider how he treats you or let him know sarcasm will not be acknowledged.
I do agree with other posts that what you are describing seems like more than sarcasm and is not really the type of treatment I would want from a partner.