Dragonskin maps aren't soloable (at least not for me) Wyvern are soloable and both drop the relic mats so that to me would be the price/demand difference. Usually with every major patch the dragonskin maps drop something useful and really are always useful but take a little more effort.

Jade's Blog: http://na.finalfantasyxiv.com/lodest.../2803251/blog/