this was not what they wanted it was a partial wrap, so therefore your google search turned up something that they were not asking for.
Given that the "attached layout" was omitted, that was the best to go off of. After all, just saying that $200 was an "appalling" for what they were wanting without context, isn't doing much. Plus, I wouldn't consider "decals" to be even partial wraps. Now, that was the term that they used, so probably wrong term, wouldn't be the first time, but there was nothing indicated by you to show anything different in the initial post, so that was totally reasonable to go off of what the Google search was showing (in my mind anyway).
Rude and unprofessional? I disagree. I basically stated how I feel about it...obviously its possible YOU allow customers to dictate your cost?
That was them stating the budget that they had. Not dictating that you do it for that cost.
I try not to let emotion get into the mix. Just have easily said, sorry, for the budget you are at, we are looking at X, for what the "attached layout" is showing we are looking at more of Y. No need to bring feelings into it. Bringing feelings into it, is actually unprofessional. Now, could it have been worse, sure, I could have distilled what you said to 3 words, conveyed the same feelings and been more efficient with my time.
I often have people come in with budgets and I let them know with that budget that they have, we are looking at this or that or just plain not feasible. Working within a budget is not quite the same as having someone dictate my cost for a specific thing. I think more people should learn to work within budgets, but I digress.