Last time I bought and replaced a heating element in a clothes dryer a few years ago I think I paid $50.00 by ordering it online.
The cost could be a little higher depending on the brand of dryer you have.
If you have to pay to have the dryer element replaced then if it's a $300.00 dryer then you're better off just getting a new dryer because it might cost you $200.00 to get the dryer heating element replaced by an appliance repair place.
It's really easy to replace a dryer heating element and you can find videos on youtube on how to replace the dryer heating element.
Just make sure you unplug the clothes dryer first.