No doubt cheapest decent performing mod is an EGO-C (twist)... especially if you only want tank systems like the pro tank II or clearmorizers etc...
I've many times found these ego-c's to be a better vape than much more expensive units (like the evic etc...)
If you want the best price/budget combo for a larger rig,
in the looks/function/price category, I give it to the flattop zmax v3...
$20 more than the vamo I think, but so much better looking and performing. Great all around cheap mod.
I havn't tried one, but the SID looks nice and is $50.
I have some very expensive mods, but most of the time I'm going somewhere I don't want to wreck a mod, I bring my zmax v3... usually whats sitting on top is worth more than the mod, and I suggest you spend your money on what sits on top before what sits on bottom.
IMO clone mods, or Chinese mods perform better than clone/chinese atty's.... the clones of the atty's usually suck.
In fact, I'm at work right now puffing on a Russian on top of the Zmax v3 and the arrow genesis on top of another v3...
You can't go wrong with them, and the display is nice on them too.. oled.