Found this tool indispensable recently - it belonged to a friend. Now I
want one too.
They come in 4" and 4-1/2" and vary in price from $20 to $100 for the
DeWalt
D28402.

Depends on how much you're going to use it. I'd say the majority of
homeowners wont use one too often.
I use my 10 yr old ($60) Makita a lot cutting, trimming tile and cutting
concrete and stone with the 3 pak ($ 9.99) diamond blades from HFT.

My F-I-L needed one for a few days work. Got the 19.00 one from HFT..whata
piece of junk..did the job but got SO hot, I had to put a glove on to hold
it.

I think its probably fair to say the $ 100 one will probably last 5X the $
20 one.