if there's really much difference between the $1.79 plugs and the $12 plugs.
Yes.
Not in initial performance but yes in longevity.
The premium plugs will have platinum electrodes and will last 60,000 miles or more while maintaining as-new performance.
The electrodes in the cheaper plugs will burn away much faster, degrading performance and fuel economy.
That said... if your goal is absolute minimum expenditure of money as opposed to not having to work on the car, the cheaper plugs will probably cost less in the long run.
Most manufacturers start out with the expensive spark plugs in order to reduce the amount of service required while the car is under warranty.
tanstaafl.