Is it my responsibility as an undergrad student to figure out if my thesis is affordable? I have an undergrad thesis idea that involves transformers. I am trying to take the lead on the idea before I contact a professor about it - i.e. figuring out exactly how I'd make it happen, and if it is realistic. The problem is that because of covid, the largest research funding I can get from my university as an UG is $500. I read a paper about a type of transformer, and I would like to apply that to an area it hasn't been applied before (my interest area). However, it seems like transformer based research is expensive.
I am worried about two things:

I don't want the professor to think I am idiot for suggesting an idea that might be big in scope / too expensive, but I truly do not know how to determine if it is too expensive / out of scope
I do want to publish first author. If this idea is too expensive, am I allowed to ask if he has any other projects for me (I can also provide him with my other interests).
Is it my responsibility as an undergrad student to figure out if my thesis is affordable?

Usually, no.  This is an example of where your faculty advisor should help you.
Do take a few minutes to research costs before discussing it with your advisor.
There might be exceptions if, based on your area of study, you were expected to know about costs already.