They are definitely cheaper most of the time. They are often just a trace on a PCB.
Product designers hate mechanical switches because they are almost always the first thing to wear out. Including a switch robust enough to last as long as the rest of the product is generally too expensive for consumer electronics.
Capacitive buttons can be made much better with some kind of instant feedback to replace the tactile feedback of physical buttons.
The problem is that adding that kind of feedback costs money. Even if it's just a few pennies per device, most manufacturers won't do it for consumer devices. That kind of penny pinching is the reason I avoid consumer grade products if at all feasible.
Yeah, a lot of microcontrollers have integrated capacitive sensing (Atmel calls it QTouch, other manufacturers have similar). In that case a capacitive button is very near free, as you only need an extra trace that is reliable to fabricate and requires minimal extra soldering.
Capacitive buttons have some distinct advantages too, primarily being waterproof and nearly infinite durability. A lot of UI issues like OPs stove are likely poor software, there is no real reason why a capacitive button would need a 700 ms pause between actions. Now, the lack of tactile feedback is a more fundamental problem sometimes, but capacitive buttons can be great when implemented well.
Capacitive also has some drawbacks. Like with this oven... They tend to be temperature sensitive, depending on shielding. Delays with QTouch aren't unusual above 120F.
Our supplier delivers capacitive switches at about $80 per thousand, resistive at $75 per thousand, and tactile at $95 per thousand.
However resistive needs fine-tuning, and really shouldn't be used in dusty or hot environments. Which adds design time and shielding costs.
In our internal research, they end up costing about equal. But we are small, so it might change at a larger scale, though I'd expect those differences to shrink.
You can include capacitive inputs on a PCB in many cases for essentially zero cost.
You also don't need to engineer attachment points into the product chassis, and assembly is easier.
In addition, they can improve the lifespan of the product because they don't wear out nearly as fast, and they don't provide ingress for dust and water.
Capacitive inputs have many downsides, but at scale they are certainly cheaper on average.
In your particular case they may not be cheaper due to other design considerations.
Product designers hate mechanical switches because they are almost always the first thing to wear out. Including a switch robust enough to last as long as the rest of the product is generally too expensive for consumer electronics.
Capacitive buttons can be made much better with some kind of instant feedback to replace the tactile feedback of physical buttons.
The problem is that adding that kind of feedback costs money. Even if it's just a few pennies per device, most manufacturers won't do it for consumer devices. That kind of penny pinching is the reason I avoid consumer grade products if at all feasible.