The faculty interview is based on the context of a department stressing on industry interaction. When asked about how to buy lab equipments and find funding, may a theorist answer the search committee that he/she does theory work mostly and therefore doesn't need much money or experiment facilities to start up? Anyway, these questions are hard for the present graduate students and postdoc applicants to answer, as they have no chance to be exposed to these things.
I currently work with CS faculty of various subfields and used to work with Chemists. It's a super hard bridge between faculty and staff regardless of field. Staff may have a form to fill out, which seems not to apply to you, but the reason the form exists is because of a simple problem... if equipment is part of your lab.... then... a new set of questioning and forms may ensue, likely as a result of federal regulations (uniform guidance in the US).
There is nothing wrong with having no other direct costs. It's simply hard for some people (not used to your field) to envision, particularly if they normally support physical sciences. So the question for you is why are they asking the question? Is it in regards to capital equipment policies? Are they anticipating space issues?
Think of it this way, when you apply to the NSF (or other federal agency) for funding, they require a facilities page. If you don't have a fancy lab, you don't need to call it out. They read your science and then predict what facilities or resources may be required. For natural sciences, you need a lot. If you state that you have an office space, access to a research administrator, general administrator, and if needs are met, the reviewers should know if that is enough to complete the work. They are looking for mismatches. Don't say you are going to perform chemistry and not describe your lab.
For what it's worth, as a research administrator at a very prominent research university, I see theory folks given a million dollars at tenure. They have a much harder time spending the money than those in the natural sciences. I personally think that senior leadership does not truly understand the field (that's a multi-layered analysis). However, across the board, the theory faculty are getting the point across regarding value. They are our top paid, top startup faculty. I don't know how they negotiate, but they communicate their value.
Don't stress over the question of capital equipment. Think about what your needs are, what your expectations are. Our theory folks want small labs (contrary to wet labs). Think about how to explain the difference to administrators and deans alike. Think about how to explain your funding strategy. Which sponsors apply to you? What is an ideal lab size? What is the ideal postdoc:student ratio?
My best faculty are thoughtful, deliberate, organized, and prepared in everything they do, and that includes paperwork. Google your institution and read up on policies from the Office of Vice Provost. Demonstrate that you know what the playing field looks like and that your field is different. If you are confident in how to describe your field and its needs, more people will trust you know what you are asking for.
If you don't need lab equipment or space to do your research then just say so and explain what, if any, support you do need to conduct your research (e.g. travel funds, a desktop computer, a chalkboard, coffee, etc.)
If there is an expectation that you will bring in external funding to support graduate students, then you need to be prepared to respond to questions about possible sources of funding and how you will involve graduate student research assistants in your research in a way that will be considered appropriate by both the funding agency and your future institution. Not being prepared to answer this question could very well cost you the position.
My response would be that:
I am a theoretician and don't require external funding for my own work so the question has never come up before. Likewise I've never had to support students so that need has never arisen. Likewise a lab. However, I recognize that external funding is important and need to learn how to do that well.
Some of the people will have a hard time with this as their situation is different. Some places need to support students with external grants, so it can't be neglected. But new faculty are, by definition, inexperienced and people can understand that, even if it needs explaining.
But ask your advisor or other faculty members for pointers for at least the most likely sources of funds in your area.