these are inexpensive because they are "plain" CZs. what makes them different from Ashas, among other things, is the fantastic diamond coating on the Asha. i'm not explaining it well, but it is that coating (which is part of the stone, not just something painted on) that gives more depth and realism to the Asha.
while these are gorgeous czs...i doubt they'd fool anyone into thinking they're real diamonds (except for the antique cuts... 'cuz they're really yummy, and most people aren't familiar enough with those cuts to be able to tell if they're fake) and, like all other plain czs, these will have a limited lifespan (maybe months, maybe a few years).
that being said, for the price (amazing!) and quality and excellent customer service from the seller... i think this guy may become this forum's go-to person for quick sparkly fixes! especially for folks who are just wanting to try out/try on different colours/shapes/sizes to see what works.
and to answer your question - if you're going for ultimate realism? no, don't do one of these instead of an Asha. if the $ of Asha is what is holding you back, go for a Winfields stone or a SparklingLizzie. yes, they're also "plain" czs but they're available in more colours (slight tint, instead of blindingly blue-white) especially if that is your "forever" ring, or will be your primary engagement ring.
since i tend to switch out and wear any number of them over the course of a month, i intend to have one of these stones set to wear as an e-ring. but i proudly wear CZs (and diamonds, too) so i'm not going for 'real' i'm just going for what sparkles best.
aaaaaaaaand, finally, i think you'll still have fun playing with these stones when you get 'em. there's nothing quite like having a palm full of sparkly rocks!