Several sellers from the Far East have been offering Lilly Pulitzer dresses at a fraction of the retail cost. Their shipping costs are often astonishing to those of us in the U.S. Understand that these are, by and large, knock-offs, overruns, or discarded samples. They do not have the distinguishing finishing marks of true Lilly fashions. They are often missing the final details of Lilly hem lace, the wonderful satin ribbon bra strap holders with snaps, and, of course, the tags.
However, a Lilly item that is new without tags is nothing to fear. Often, retail stores will remove the tags, explaining that it is necessary for their "inventory" accounting. I have bought many Lillys NWOT tags from Lilly Signature and Retail stores, as well as on eBat=y, and have never been disappointed. Just be careful that you know your seller from his/her feedback and location, and you'll be fine.
On the other hand, if you have no problems with seconds, unfinished Lillys, and samples, it is entirely up to you to buy from overseas vendors. But please remember that Lilly Pulitzer (bless her heart) will receive absolutely no income from these sales.