JCtx

I'd defnintely put a filter in there. In addition to all the reasons above (all valid), your car would be much less dusty inside.
Having said that, what makes the Lexus filters so expensive is their treatment to prevent odors inside the car. You can buy a dirt cheap filter on Ebay without that treatment, and at least keep the filtering option. Or you can cut your own, as somebody pointed out. Just have some kind of filter in there. And keep in mind all the crap that clogs your filter would end up in your car, lungs, and clogging internal parts. Later.