My own needs and experiences, David, are not a good guideline, so it depends on what you want.
I'm in two Y/P's: SW B'ham, Bromsgrove & Redditch and SE B'ham and Solihull. The cost for both in the NCCA Corporate Heading is £114.00p
It does not generate a terrific number of enquiries, a common criticism of Y/P in general, but my experience is that the leads it does provide tends to be more serious enquiries and barely any price-shoppers.
If I did not receive any leads at all, I would still have a presence in Y/P as it is still, probably, the first place my existing customers will look if they've lost my phone number.
I regard Y/P as a necessary evil so have in recent years tended to use the lowest cost option ie NCCA Corporate Advertising.
Safe and happy cleaning
Ken