Today’s B&H Photo Video DealZone (one-day deal) is the Tiffen 82mm Variable Neutral Density for $79.99, after a manufacturer (Tiffen) $20 mail-in rebate. This 82mm filter size is very popular as it fits the 24-70 II, 16-35 II, and 16-35 III.
This is an affordable way to get into ND, and good value (assuming you don’t want to spend $300-$400 on a professional ND filter system). Deal is today only or until sold out.
Not familiar with the variable systems, curious, what are the drawbacks? I’m going to guess increased ghosting and or CA? Diffraction? I would guess it works fine for someone that is short on cash but also would like to test their hands at an ND system? Can this be effectively put in a step ring to be used on smaller diameter threads?