I'd buy. Factors are a bit of everything. I don't care paying for a good quality product, as long as the pricing is reasonable. I'd rather pay a bit more for something good than put money out for something that ends up being a POS.
Compatibility/QC is also a factor. If I drop hard earned cash on something, I want to be able to use it as intended without having to break out the Dremel to fix stuff first.
And lastly, variety and/or custom work would be important too; if you browse what's out there now, there's a lot of variety for slides, but they're all intended for a somewhat restricted number of guns (WA SVs, TM Hi-Capa, etc) and only a very limited selection for other guns.
In my particular case, I've been trying to find a metal slide for my WA Striker 45 (single stack 1911 with a bushing); because of the shape (its an SV style slide) and also being single stacked and using a bushing (unlike SVs), and especially because I'd really like to find one with Springfield markings... no luck.
(here's a couple of pics if you really care: 1 2
(shit you can make one of those for me, i'll pay you)