Limited editions are so important at least to me... I'm MUCH MORE likely to buy a single if something extra comes with it... Heck, I've bought some Maki singles because the extras were so cool (Uwasa no SEXY GUY tin box etc.), I bought the H.P. All Stars single for the mini PB coming with it... Datte ikite kanakucha came with 5 fricking posters!!!
Extras make people buy stuff they wouldn't buy otherwise. T__T I wouldn't be surprised if some people didn't buy Nacchi's two latest singles because there was nothing fun coming with them. And I don't think Yuko's single will sell very well, either.