For something fairly simple like a cast, that can still end up more expensive than the clinic option though, depending on your insurance. ER co-pays and co-insurance can be pretty high. For example, a typical ACA/Obamacare "Silver" level plan in my area has 20-40% co-insurance on an ER visit (until the $5k-10k annual out-of-pocket max), which can easily be more than whatever you'd end up paying for the non-ER option to set a broken arm.