I have a 2012 Limited and both of my front ones were dead when I bought it last April. I bought 2 new ones off of Ebay for about $30 each. Took me about an hour and a half (1.5 hours) total to do both doors and haven't any issues ever since except we forgot to hook up the manual unlock (for the key) on the driver door. Way better than the $700 the dealership wanted.
While you're correct that getting the parts from eBay and doing it yourself is certainly the cheapest way, I was mostly curious if the Toyota dealership actuators in 2018 have any actual improvements in quality and lifespan. If $600 per door gets a permanent fix that doesn't require me to disassemble/reassemble every door in the 4Runner repeatedly, I'd gladly pay it.