I have purchased the John Murphy plugin, both Bollinger plugins and the Alex Elder plugin.  I think all seem to work within the scope of their authors' approaches to the market, but if I had to do it again, or choose just one it would be Elder's far and away.

Having read his books and understood what he's getting at, I use his plugin on my default chart designs.  However, I'm heading more toward a mechanical system design vs. his discretionary/mechanical approach so will likely incorporate more-specific entry/exit strategies than his, which rely more on subjective decisions after indicators trigger a "take a look at this" condition.  No matter what approach you take to the market, his books are well worth reading for the psychology perspective alone (but there's a lot more to it than that).

And FWIW, the best price on the Elder plugin is at his own site elder.com.

Not disparaging the Murphy and Bollinger packages; I just don't use them much.  If you like the approach of either or both men, they're both worth having.

3-for-2 is a decent deal, but if you don't need all three it's not.  I did some web searching and found good prices on my plugins two years ago vs. buying directly from Equis.

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When you see that in order to produce, you need to obtain permission from men who produce nothing - when you see that money is flowing to those who deal, not in goods, but in favors - when you see that men get richer by graft and by pull than by work, and your laws don't protect you against them, but protect them against you - when you see corruption being rewarded and honesty becoming a self-sacrifice - you may know that your society is doomed. - Ayn Rand