Can I install a wiper arm from an older Ford Focus on to my 2013 Focus

I wouldn't do that just yet,but I do see your point on the prices at local parts stores. I see that there are several designs for your car and don't know which type you have,but here is one comparison of the prices from Autozone and RockAuto.com. Autozone Bosch Evolution Wiper Blade - Front, Beam Design-Part Number: 4844 Fits driver side and passenger side. 28" wiper blade.$ 22.99 each X 2 = $45.98 plus tax,around $50.00! Rockauto.com Bosch Evolution Wiper Blade- Beam Design- Part Number: 4844 Fits driver side and passenger side. 28" wiper blade $9.56 each X 2 = $19.12 plus $8.99 shipping,4-5 business day delivery Total price NO sales tax,=$28.11! same exact blades for around $22.00 LESS!!! Now Rockauto.com has all brand name blades and several different styles like,TL2, 9mm Hook, 9x4 Hook, Side Pin (22mm), Side Pin (17mm), Pinch Tab, Push Button (22mm), Push Button (19mm),etc. I'm sure you know which style you need and they also have the one for the rear,12" if you have the Focus Wagon? so go to Rockauto.com and check out their selection and prices.website is very user friendly.

Check out eBay - them wiper blades from China are as good as you can get - they simply last longer - on my vehicles - and I've tried 'all' of the so called premium brand wiper blades. I can buy '3 pairs' from eBay for what 1 pair cost here at the parts and retail stores. Been using them now for 4 years.