Air purifiers are capable of removing PM2.5. Most people can get one under $150. I found that unused second-hand ones are abundant on Craigslist, eBay, etc. Get one that doesn't have ozone. I found that the Winix's ozone runs even when turning it "off".

There are reviews online that also take into account long-term cost (including the price of the filters themselves and how often they need to be replaced).