With wine kits...you pretty much get what you pay for, and what you pay for is the total amount of dissolved solids in the concentrate. That's why U.S. Elite can charge as much as Wine Expert for their 6.3 liter kit vs a 15 liter kit. You get 6 gallons of wine out of each of them, but one is more concentrated (or has more dissolved solids than the other).
The really cheap kits are usually sweet wine kits, they are lower in ABV, and have you sweeten the wine with an F-pack. That allows you to drink the wine early.