Buyers should be very aware that with the prices of militaria rising significantly there is great temptation for unscrupulous sellers to misrepresent items or for unknowledgeable sellers to unwittingly sell reproduction items as real.
For instance, reproduction AATTV (Australian Army Training Team Vietnam) patches - listed as 'repro' - can be picked up for very modest prices. Artificially aged - washed, bleached, 'dirtied-up', sewing holes applied - they may pop up later, listed as genuine items. Genuine AATTV patches are very, very rare, and any dealer offering more than one once in a 'blue moon', either has been extremely fortunate to somehow find an excellent source of these rare items, or the items are just plain fakes.
There are a number of militaria web sites where such things as badges, patches etc. are discussed and where collectors can educate themselves on how to tell the fakes from the genuine items. Read up, learn from the experience of others, don't get taken in, and get the most out of your collecting budget.