Costs vary by the cartographer, but an 8x11 sheet (A4 in Europe and elsewhere in the world) by a professional will likely set you back from several hundred to over a thousand dollars US. Cost depends on the amount of detail, whether or not the map is in color, and the amount of layers and finishing required among other things. Best of luck to you.
The cheapest (but most work intensive route) is to look at the tutorials on this site (there's a forum with tutorials in it) and ask pros like RobA, Torstan, Turgenev and others for pointers and do it yourself. Print shops and specialty printers such as Gamerprinter (no, I'm not shilling for him, but he does good work) can print your map out, even at large sizes. Note though, that a really large map may cost well over a hundred US to several hundred to print.