Soylent 1.6 (powder) is "$1.93 per 500 kcal" where 2000kcal is what most people eat a day. If a meal to you is one third of 2000kcal, it costs 1.93 * ((2000/500) / 3) == $2.57 per "meal."

Soylent 2.0 (drink, bought because it's "more convenient") is "$2.69 per 400 kcal." If a meal to you is one third of 2000kcal, it costs 2.69 * ((2000/400) / 3) == $4.48 per "meal."

So compare either of those to either your dinner or snack expenditures. To me it seems that 1.6 can save you money on dinner, while 2.0 is intended to help you save money on "snack time".