Synthetic vitamins are definitely cheaper than naturally derived from natural sources. however some issues need to be addressed : 1. most vitamins synthetically produced are biologically effective as those of natural occuring. one well known exception is the synthetic vitamin E is not recognised by the body as Vit E, therefore the absorption is 50% or so lower than natural Vit E. Companies who claim to use natural resources, usually does so, but needs to be verified, esp on it\'s credentials. Some third party organisations does a lot of verification, such as consumerlab.com, nsf.org, etc. Even so, it is very hard to formulate the right amount from the natural sources, unless it\'s extracted. Those which include other phytonutrients, or utilises the whole part of whole plant as concentrates will definitely need to top up or fortified it with either extracted single vitamin or uses synthetically produced ones. nothing wrong with that as the key thing is the numerous phytonutrients that are beneficial.
2. The product consists of the right amount of claimed subtances on the labelling. againt, the few websites i mentioned do all the tests to certify such claims by manufacturers. however, full information is for a subscription.
3. Reputation and history of the company is another factor. A company with good track of records providing quality stuffs is more important. if one company has product(s) recalled back due to problems in manufacturing (QA/QC), or the amount of ingredients is either too low or too high, causes more harm than benefits. Contamination of raw materials, for e.g. lead level in certain sources such as herbals, are deadly. it doesn\'t matter on the price, but more of quality and efficacy. you may save a buck or two buying a cheaper alternative, but you may ended with paying more than you can earn a year for therapy, surgery, correction, etc. health is invaluable.
although this reply is rather late from the first post, hoped future individuals may benefit from it.