Like many investors with Wal-Mart Stores Inc. (NYSE:WMTA), Target Corp. (NYSE:TGTA) and The Kroger Co. (NYSE:KRC) stocks in their portfolios, Costco Wholesale Corp. (NASDAQ:COSTB) shareholders also have been worried about the impact of the upcoming Amazon.com Inc. (NASDAQ:AMZNC) Whole Foods Market (NASDAQ:WFMC) merger.One Wall Street firm says enough is enough. Raymond James just raised its rating for Costco shares to “outperform” from “market perform.” This based on a prediction that Costco’s business will not be “materially impacted” and its sales growth will remain solid.Related: AMAZON VS. WAL-MART – FROM GROCERY WARS TO CLOUD WARSFrom Panic To PurchaseRaymond James analyst, Budd Bugatch noted that with Costco shares falling 13% through Friday and the subsequent downgrading of the retailer by multiple Wall Street firms, now might be a good time to buy.In a note to clients Bugatch said, “Admittedly, even with the recent pullback, Costco still trades at a premium valuation to the overall market and its large retail peers. Nonetheless, its business model remains intact with healthy membership growth and strong renewal rates.” According to the analyst, “Amazon’s agreement to buy Whole Foods, when consummated, will add a new dimension to the grocery business (but) does not materially impact Costco’s unique business model, and we would be buyers on COST’s recent weakness.”Different StrokesBugatch suggested that Costco’s business is “vastly different” from Whole Foods given the fact Costco customers tend to buy in bulk. He also noted the “treasure hunt” nature of a Costco shopping trip in which customers come in the store for a set number of items but can’t resist unexpected bargains.Finally, the analyst said Costco has potential to increase sales and new member roles significantly by opening new stores in coming months and years. He estimated Costco would increase its sales to $139 billion in 2018 from $129 billion this year. Because of this Bugatch initiated a price target of $173, a 10% upside from last week’s close.Shares Are UpFollowing the upgrade by Raymond James, Costco shares closed Monday up 1.95% at $160.20. This is an indication of investor buy-in of Raymond James’ suggestion the stock has been oversold as a result of the Amazon.com, WFM announcement.Since Costco makes most of its profit from membership fees, which account for 75% of earnings for the company, Raymond James believes Costco will be able to weather the storm when the Amazon.com, Whole Foods deal is finished the real impact is felt.Related: ONLINE SPENDING AND AD BLOCKINGA Grocery GlitchFor those who believe Amazon will win an all-out war due to the likelihood it will offer delivery of groceries, something Costco doesn’t have, there actually is a way to have Costco products and groceries delivered – even if the buyer is not a member.That’s due to a little-known but growing group of delivery agents that will send a shopper to the store of the consumer’s choice to buy items and bring them to their house. One of these companies, Instacart, works closely with Costco and will send a shopper to the store – even for people who are not Costco members.