Thaluikhain said:
Varies quite a bit though. A Sisters army of all metal models (and limited range of those) is quite pricey (hell, you can still get the old metal guard), but on the other end of the scale you could get the Betrayal at Calth boxed game and get a SM army relatively cheaply.
Of course, and that's the case with pretty much all miniature games. But let's go for the cheapest possible army that's tournament legal for 40k and FoW:
Flames of War: 10 Panther D tanks (45USD per platoon of 5) and a platoon of panzergrenadiers (45 USD) will set you back about 135 USD, assuming you buy straight from Battlefront. From that you will have 3rd SS Panzerkompanie list at slightly over 1750 points (3rd ed pointing) with 1,5 Panther platoons, 2 HQ tanks and a full platoon of panzergrenadiers. Not exactly a great list, but fully serviceable if you face a Soviet armor list. This is roughly equivalent to getting the 80 USD starter boxes and adding in a support platoon of your choice.
40k: If I get the premium deal for my Space Marines, I get the Dark Imperium box and split half with a friend who wants to do Chaos. at 80 USD I am then roughly halfway to a 1500 point list, with 3 meager tac squads, 1 minimal assault squad and a decent HQ. Adding a dreadnought and a tank will
probably put me close to the point limit, especially if I kit everything out to the max with upgrades. But that's 57 USD for the predator and another 46 USD for the dreadnought. So that's over 190 USD for a decent Space Marine list.
In my own comparison I had a 1000 point Space Marine army that comprised 2 tac squads, 1 devestator squad, 1 assault squad, 1 rhino, 1 dreadnought and a Captain. That's 280 dollars just to get to the bare minimum needed for the smallest games. For comparison my Flames of War army comprised 1500 points and had 2 Udarny Strelkovy companies, a anti-tank gun company, 5 T-34s, 3 ISU-152s and 8 Katyusha rocket launchers and that came in at roughly 200 dollars, with enough spare models to comfortably get me from 1500 pts to the tournament limit of 1750. On top of that FoW allows for proxying 1/3rd of your army in any Battlefront sanctioned tournament, as long as the proxy is a model of the same unit/vehicle and to scale, which means that I could have cheaped out by getting Zvezda or Peter Pig miniatures for my tanks and Katyushas instead, which would have saved me some 40-50 dollars.
For Tournament legal lists (if we accept official tournament limits as the "standard" game mode your list should be built for) Warhammer is always the most expensive by a fair margarin. The comparison with FoW is very unfavorable in terms of price to game presence impact, and FoW is generally considered to be really expensive by military miniature games standards. If we compare to a game like X-wing, where you can get a functional list for around 100 USD, 40k is downright robbery in comparison. And that's even before we get into things like the premium price on GWs own modelling and painting supplies when compared to competitors like Vallejo, Army Painter etc..