it should not hurt them but i wouldn't put the over any markings. i have purchased several that had them on the acl lables. they can be difficult to remove sometimes.
Just like removing decals from a car; use a hair dryer. It loosens the adhesive and the decal peels right off in most cases. Then get rid of the remaining adhesive off with either goo gone or wd-40, if that could be done safely.
If the price tag is on a label, be ultra careful with the hair dryer so as not to mess up the label.