I'm not sure that the cost of hop ups would even factor into a reduction of weight. If you slap a Lipo in your car right now, any car...your under the standard weight limit. So if the limit gets reduced, no one would "need" to get lightweight parts.
If a car like the TA05R can come in well under weight with just a Lipo and no hop ups, I think all these people running at big events will be okay running X-Ray, Schumacher, Corally, etc...