Perhaps it is easy for me to say, because I'm merely a customer and not a producer, but nonetheless if this problem of recasting is really getting bigger it is time to adapt the business model.
Now you producers take big risks by having high initial cost for the master and boxart. A recaster needs just one copy and he has the same product with much reduced initial cost. If the likes of eBay are not doing much (which is disgraceful in my view) one is left with few means to do anything about it.
Having said that, you producers have one thing that recasters do not have: innovation. The recaster by definition does not bring anything new into the market. There will always be some base level interest in old kits, but are we not most motivated to buy that latest new release? A recaster is not going to bring that excitement.
I wonder if it is not time to move to a different business model. One like kickstarter, where customers invest in the original cteation. The whole thing only happens when the investment is covered. For example, producer A shows a concept drawing of a new figure and announces it intends to have it done by sculptor X. Only once the investment has been committed to, is the figure actually sculpted. Original investors get extra heads and other goodies, anyone buying the figure later will get just the basic figure, to ensure there is an incentive to pay up first.
This model would have the extra benefit that no lemons will be produced. If a figure attracts insufficient interest it will not be made. Only the hits will get done.
A recaster can of course get his hands on such a figure as well, but that is less relevant now, because the investment has been covered already. In fact, subsequent figures couod be offered at a reduced price by the original producer, meaning it will be harder for a recaster to undercut the price.
I totally agree that recasting and, even more so, buying recasts are very low things to do. However, if it is really killing you, perhaps it is time to adapt the business model.
I'd be interested to hear comments on this; on why it could or could not work.
Cheers
Adrian