Wilson makes decent parts, not the best in the industry, but better than average. There are so many variables when it comes to gun parts, no matter who makes them. If they're "drop in", that means the specs are looser so they will fit a variety of guns. If you want a really good fit, you'll buy "oversized" parts and have them fitted. Now you have the price of the parts plus gunsmithing. You could easily end up with a "$600 toilet seat." If you get a gun that is worn or made out of spec, you may be sadly disappointed even with the most expensive parts.
When it comes to generic parts like springs, sights, grips, etc, you pretty much get what you pay for. Often the standard factory parts are the best price for the quality. The parts to avoid are the "no name" stuff you see at gunshows or in cheap catalogs. I buy most of my gun parts from Brownell's, partly because it is so convenient, but mostly because they stand behind their products, no matter who makes them. A word of caution: most parts are sold without a warranty or have a warranty that states once the part is altered, the warranty is void.