Yeah that's what they cost today. I've also seen them at 1/3 that price, depending on when you look.I prefer the price of the Acoustifeet Mike !
Yup, you definitely want something that screws on.If its a power amp with a big transformer I generally go for something like this
Large Heavy Duty Rubber Feet x 4 for Peavey Amplifier Cabinet guitar amp speaker | eBay