A lot of places say "click here to see where we are" and have it as just a link to a search for their postcode/address on Multimap/whatnot - so you aren't actually publishing the map, just making it very easy for people to look you up. I can't see how there would be any cost involved as they get the benefit of extra links and extra visitors.
Yeah, I have just discovered the 'link' button on the multimap site, thanks