I would definitely be careful here because vintage brass mirrors are super heavy and fragile, so shipping them to Chicago is probably going to cost the seller a fortune. If you push too hard on the price, they might just back out to avoid the risk of it breaking during a rushed shipment. I have seen sellers get pretty defensive when buyers ask for huge discounts on fragile items. Before you message them, I would suggest looking into a couple of details. Is shipping already included in that $210 price tag, or is the seller charging shipping on top of that? Also, does the seller seem to have a lot of items, or is this just a casual shop? Knowing those details helps figure out how much wiggle room you actually have without offending them. If shipping is free, asking for $150 is basically asking them to take a huge loss after postage and packing materials. If you decide to wait it out a bit to see if the price drops naturally, you should check out PriceDropCatch, it's a free tool that works right in your browser.