This depends on a lot of factors : the bdu, aeg, etc.
for instance, my first gear was a flectarn bdu with the matching chest rig cost me about 150$ (I bought it at R3CON1's store); then I spend 600$ on a G&G AK-47 with 4 mags and 2 batteries. for goggles, I used shooting glasses (15$ and very sturdy construction) . I also owned a WW2 Bulgarian steel helmet which I just put an helmet cover on (5$). For boots, I just used my regular hiking boots. I spend 150$ for a TF-11 as my GBB side arm.
Overall, my first kit cost me roughly 900$ and it was fairly decent.
For my second kit and main kit, I field a Waffen SS NCO impression which was much more expensive (After 2 games, i talked with a guy fielding a waffen SS impression and I succumbed to the temptation
): my impression is complete and costed me around 1500$ ( 500$ for my mp-40 and 9 mags : 100$ for a m42 steel helmet, 250$ for the bdu, 50$ worth of insignia and decals, 300$ of field gear (gas mask canister, mag pouches, ss enlisted man belt, bread bad, shovel and carrier set, a nva canteen) : 70$ for a pair of NVA jackboots, 40$ for a deactivated m24 grenade. 150$ for the winter parka
for 1.5 K, i have an almost complete impression of good quality (missing a zeltbahn, a A-frame assault pack and a frame bag)