I don't know if this is cost effective enough for you, but Nature's Gate has some good conditioners and I've seen them for around $6.50 USD for 18 fl oz/ 532 ml. If it's a really well formulated conditioner, you actually need to use much less product so the cost can often be the same as buying a cheaper conditioner but the results much better. I am currently using Nature's Gate Jojoba conditioner and I find it very moisturizing.
Another thing you can do to increase the amount of moisture in your hair is homemade treatments such as olive oil + honey. This will greatly increase the moisture in your hair and be cost effective as well.