Did you try modifying step 2 to something along these lines:
"Great idea, I never thought about it, we really need <something>! Problem is, this particular model of <something> is not the best and will not do <something that something is supposed to do> very well. In fact I remember reading bad reviews about this. But fear not! We'll go home, spend some time reading review sites and will find a really good version of <something>."
This will buy you some time, and might even look that YOU want it, which might even make it less appealing to your other half. Now, find a really expensive model of something, but at such price point that the rationality wins, even in someone who usually does not listen to your arguments (step 2). YMMV, but sometimes this tactic works out quite well.
"Great idea, I never thought about it, we really need <something>! Problem is, this particular model of <something> is not the best and will not do <something that something is supposed to do> very well. In fact I remember reading bad reviews about this. But fear not! We'll go home, spend some time reading review sites and will find a really good version of <something>."
This will buy you some time, and might even look that YOU want it, which might even make it less appealing to your other half. Now, find a really expensive model of something, but at such price point that the rationality wins, even in someone who usually does not listen to your arguments (step 2). YMMV, but sometimes this tactic works out quite well.