It's not the key that costs big money, nor is it the transponder inside the keyhead.
The huge price tag on a replacement key for a modern Toyota is the technician cost, computer rental and programming time for your Toyota dealer to plug in their laptop for approximately 15 minutes so that the car will recognize and respond to the new transponder within the key.
Your local friendly automotive locksmith will clone your existing transponder if possible, reprogram your car for a smaller number if possible, install a transponder bypass system if possible, or tell you to suck it up and go to your Toyota dealer.
Just remember that if you lose your only key whilst you're in Walmart you get to pay the towing fee to your dealer before they start the clock on reprogramming and rebuilding your computer and the physical car locks. Total cost for that service usually runs into four figures.
Also, another transponder key doesn't stop the jokesters from moving your car 3 rows across and 2 spaces down like they do with everyone else. Although with a Yaris they could just pick it up and hide it in their pocket