I'm tired of the prices as well... but I don't think limiting yourself to a questionable... potentially dangerous... substitution game is the right answer. The prices are the prices, buy what you need... and be done with it. If LPP's are $100 a brick, and LRP's are $100 a brick... I don't see where 'consolidation' is a reasonable avenue.
Just because it can be done, doesn't mean it should be done. You post over-pressure load data, THR asks you to post a disclaimer with it... because 'Safety First.' ...yet, here we are talking about using LRP's in handgun cartridges....?
I think Sierra has it right...
To sum it all up, do not substitute SPP for SRP or LPP for LRP at all, period. It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.