An ignition coil for my car can be had for a princely $17 on RockAuto. The life hack here is to not get ripped off by a mechanic having it put in; in most cars us Poor People are likely to be driving (i.e. not an Audi, Lamborghini, or Porsche) any garden variety fool with two thumbs and a $20 Harbor Freight socket wrench set can swap out an ignition coil in their own driveway in about 5 minutes.
That's fair, in most cases I would have done it myself. When a coil pack died on my last car, we harvested one from a dead car on my dad's property. I took it to a mechanic because I thought it was the transmission. By the time I got the diagnosis, I was afraid that the other pack would die driving it home to fix myself
The majority of check engine lights that come "out of the blue" are emissions related failures, usually a leaky (or unscrewed) fuel cap, bad O2 sensor (~$40) or similar. Learning how to Google this stuff for yourself will save any vehicle owner hundreds of dollars instantly vs. spiraling into anxiety over having to pay a mechanic for what is, in most cases, something incredibly simple.
And it will at the very least let you know if it's serious. I had the check engine light it was that the emissions testing wasn't working properly so I was at risk of potentially burning more fuel that normal. Whoopdie shit. Ran through some highway and city driving and it cleared itself.
Of course now my airbag light is on FML. 2012 car I think the circuits are going.