There are lots of reason why clothes dryers stop producing heat, mostly customers assume there must be a problem with the heating element but thats only half the story.
Here are the top reasons a dryer wont produce heat or dry clothing

1, heating element,
2,high limit thermostat open, ( usually from a blocked vent or overloading).
3,incorrect power supply to dryer, ( bad breaker, bad outlet, bad power cord,)
4,bad thermostat or thermistor
5,no voltage from timer, (usually see this on dryer produced from 2010 onwards)
6,igniter coils or flame sensor (gas dryers)
7,bad heater relay(s) on control board,
8,centrifical switch failure on motor
9,broken or damaged wiring harness
10,blocked or restricted exhaust vent (dry produces heat but takes forever to dry).

So as you see lots of reasons why dryers fail to heat or dry clothes, all of these can easily be diagnosed by an experienced repairman.

Cost to replace heating elements

Most modern HE dryers still use a 2 wire element, (Samsung, Whirlpool, Maytag,Kenmore,Frigidaire, General Electric, cost to replace average around $145.00 parts and labor included.
Some modern HE dryers now use a more expensive 3 wire heating element, (Frigidaire, Samsung, Whirlpool, LG, average cost to replace around $175.00
Most traditional dryers, Whirlpool, Kenmore Maytag etc have a common heater, we replace those for $109,00 parts labor included.

High limit thermostat replacement on any HE dryer is $99.00 out the door
High limit thermostat replacement on traditional dryers is $69.00 out the door

Thermistor or thermostat replacement is according to the brand of dryer, expect to pay from $99.00 to $119.00

Gas dryer repairs will usually be around $99.00 but some igniters can run up the repair bill to $149.00

Bad relays usually requires a new control board which can be expensive, our cost is $69.00 plus the board

Harness repairs are usually simple and we charge just the service call.

Lastly and most important, dryers which have a blown high limit thermostat usually need the exhaust vent to be cleaned, no point in replacing the thermostat where the vent is blocked, the thermostat will just blow again quickly and there is a risk of fire.

Dryer vent cleaning for a single story building starts at $70.00 with multiple floor dwellings via estimate.