Regarding the cost of a DMCA notice.... it doesn't cost anything, really. The name is an abbreviation of Digital Millenium Copyright Act and all you need to do is have a lawyer send a notice following the requirements listed in the DMCA. The lawyer may cost money though, unless you already have one on retainer. There is a company and site named DMCA which is providing a service for sending these notices but they are simply capitalising on the name DMCA. It's quite possible a lot of copyright owners use them but they are not required for sending such a notice.
The lack of a cost to send these notices and the extremely low risk of getting caught when you send an incorrect notice is what makes the whole DMCA a mess. There are some good things in the Act for protecting sites like RLFC and CC but you will typically need to pay your own lawyers to fight back which is costly, so most small sites simply submit and remove content or shut down entirely when served DMCA notice.
I should mention that I am not a lawyer but I find the topic interesting.