Does the value of an item that I enchant increase linearly? What I mean is, when I enchant a gold ring with a waterbreathing enchant and use a petty soul gem, it increases in value from 75 to 301 at my current skill level. So if I were to enchant a gold and ruby ring (value of 700) with the same enchant and the same soul gem, would it increase by 226 (301-75) as well?

never bothered to calculate, what i can tell you is that some enchantments are way cheaper than others, in fact i only use sneak enchants when i do it for selling, seems to be the highest value