Well most of the riding crops you see in a serious tack store should come with more than just a price tag, there may be a stiffness rating of some kind like 1-5 (five being super flexible) and a little information on what type of crop it is, where it was made and out of what materials.

Some hand crafted crops leather and wood from France can run upwards of 200 dollars. (a little pricey for most of us)

Most of the ones people find in non-bdsm specialty stores (lingerie stores and the like or the standard farmer's market that doesn't specialize in riding tack) will most likely be the cheapo 4 dollar crop which is ussally rated at 4-5 which is the new standard for use of late thanks to peta and others at least at some tracks and equestrian centers lol, since the stiffer the crop the more likely it is to leave welts on the horse in the untrained hand. The kind of crop you find in a novelty store or a lingerie store will most likely be no different than the cheapo ones, only price wise marked up like crazy.

Also keep in mind, some of the smaller bdsm supply stores or places that sell bdsm supplies in local markets will put things out for sale that are home made (especially if they themselves are into bdsm.) This doesn't mean they automatically suck or anything, in fact sometimes its quite the opposite especially if its made reinforced and made to last, after all, one usually uses their crop much more frequently and quite a bit harder in bdsm during impact play than they ever would on a horse.

I advise either going out to a bdsm specialty store or an equestrian supply dealer and hand selecting your crop as opposed to ordering online regardless. (hence why I'm not linking you any one site's page) The only way to find the one that will be a good fit for you is to give it a swish or two in person.