Maybe charge them a reasonable fee for the removal, like double whatever you charge for the gilded lettering, but also make it clear to them that this was a one-time deal of a price and future issues (that are their fault) will be billed at the standard shop rate. IE: it's only gonna cost you 60 bucks this time, but if we have to do this again it's going to be 300 for example. That just might put them on notice to be a little more careful at their proofreading, but still not cost you the future work. Just my 2 cents worth (of materials?)