Do you have a Salvation Army Store near you?  Or a consignment shop?  I frequent our SA Store and there are currently a couple wedding gowns of questionable class (so many beads and bling they must weigh a ton

) and some pretty hideous gowns.  Extremely cheap!!!  If you do have any, keep an eye out for half-off day.  Good luck - that's a super idea.  You must post pics.   
OOP!  Just reread your OP.  Missed the last sentence, lol.  I'll be happy to check back at ours.  I think the one dress was about $45 and a size 10 or 12.  But, my memory only lasts about 20 minutes, so I'll have to go back and check again

.