" I am looking for a babylock serger. I saw a serger at Costco for $200—is there anything cheaper?"
The simple answer is, "Yes."
But let's take a deeper look....
Sergers range in price from $88 (no-name brand, no-name website) to $4000+ (industrial). The lowest in the price range, though, involves high risk, since there's no evidence that the serger or the website is reliable. On the other hand, you probably don't need an industrial serger for personal use at home.
For the specific serger you mentioned (Brother 1034D), Costco offers the lowest price. The only other place that sells this serger for $200 is refurbished (although the company throws in a few small accessories for free).
On Amazon.com this serger received 4.7 out of 5 stars (126 reviews). On epinions.com it received 4 out of 5 stars (9 reviews). Lastly, consumerguide.com rated it a 3 out of 5, stating that it peformed better than they expected.
Since you mentioned Babylock sergers, I checked into those as well. Information online is hard to come by, because they are only sold at a brick and mortar store. Used Babylock sergers on eBay ranged in price from $300 to $2000. Consumer guide rated them as top of the line. I called a local sewing store near you to find a little more information. They have a higher end Babylock serger, which is their most popular, on sale for $1299. The lowest end of the Babylocks is on sale for $299. You can visit the store to try out various sergers.
Bottom line: In my opinion, the serger from Costco is the best deal out there. Besides getting a good price, you also have the security of Costco's return policy. If it breaks or you don't like it, you can always return it...no questions asked.