Why are so many IRS Betas for sale
While they were/are a great speaker in times when Infinity was on top of the tree, those products have now got many years on them, and most by now are in need of a full resto job, and that is "very" expensive to do on these, unless you can do it yourself, then it’s just expensive and time consuming. So owners decide to flick them before they start costing them money.
If you can find a pair that has been fully restored by someone who knew what they were doing, then that a pair will serve you for many years to come, and sound great to boot. But these Infinty’s IRS and Betas also need boat anchor amps to get them going to their best.