$50 on Bones for a handful of orcs and skeletons plus some giant spiders and some heroes. Or drop the skellies and add trolls and/or ogres. Download Swords and Wizardry Core. RPG! Or if that's a bit heavy, try Fubar Fantasy RPG. Also free!
Alternatively, the orcs and skellies, plus Ares or, if you prefer lite and slightly random rules, Song of Blades and Heroes, where everyone has only one stat for simplicity but there are six-and-counting books of all the special abilities you need when everyone only has one stat. But it is freaking fast to play. Either of these set you back about $15 for the PDF. But really you're better off getting more miniatures for the free postage anywhere, and wearing the $15 or thereabouts for decent skirmish rules.
Last option! Don't want to choose between RPG and skirmish, OR want to run warbands with experience tracking and all that jazz? Goalsystem Delves. Again, $15 for the PDF.
Of course, my personal best-ever value proposition was the Vampire level pledge in the Bones Kickstarter, $100 for enough miniatures to run miniatures-heavy RPG campaigns from now til you die, came with Swords and Wizardry Complete PDF.
EDIT: I don't think GW is evil or their fans stupid, I just do not have the money to buy their stuff and, to be honest, I find their games just don't suit my tastes anymore.
Edited by smokingwreckage, 05 February 2013 - 06:03 AM.