My disdain of beer signs is usually less about the signs themselves, although they are--at least in more recent years--not built well at all, but more about the typical customer who seeks a beer sign repair. Except for the true collectors who have a genuine vintage sign and understand what is involved, the typical customer, to be blunt, wants it fixed but doesn't really want to pay for it. When you quote the cost of a new tubing unit, the response is often along the lines of, "the whole thing only cost a hundred dollars!" and so they simply won't foot the bill for a proper repair. Again, there are some who are serious and are willing, and willing to learn why the cost is what it is.....but more often not, so I typically would not see the wisdom in trying to compete in the low ball arena.
However, there is some merit to try and obtain popular units from the (often free) broken signs that turn up and save them as a possible future sale of a used replacement unit. There is also merit in keeping patterns of anything you do end up making or even potentially making patterns of all the units in a rare old example even if it is only in the shop for a transformer....simply because you never know when they might come in handy.
Lastly, although many are probably long gone, I have seen some beer sign patterns and jigs (YES, many were jig bent!) that were discarded by the manufacturers when they shut down or moved on to a new ad campaign....so you may find some that way as well.