Smart Parts grips are the single best product to ever come out of that "wicked" company, imho.
They fit well, look good and come in a large variety of color schemes. I have the SP grips on all of my .45 and Sheridan-style grip framed guns; Blazers, Typhoons, you name it.
Very good product.
As for the over-abundance, the Gardners probably had them made in China or somewhere in very large quantities, hence the surplus and low price.
Most likely, it is an effort on the part of "Satan Parts" to put all of the small-time wood grip crafters out of business.