What is the average price for a good prong collar? ?

I'm going to buy one for my dog Ellie because I think it would just be alot easier and better than using an easywalk harness (my mom's choice, she believes that only my older dog needed a prong and Ellie doesn't) She said that if I want to get Ellie one, I have to buy it myself ... Anyways, how do I know which is a good price? I've seen some for about $5 at Menards(I'm not getting one of those, they seem very weak and the prongs were extremely dull) and then i've seen some for$35 at Petco and Petsmart and prices in between that range. Which is a good price? Thank you!