* (Updates with investor quote; notes limited number of shares being bid up): AMSTERDAM (Reuters) - Shares in Adyen, (ADYEN_w.AS), which handles the payments backend for Netflix (NFLX.O), Facebook (FB.O) and eBay (EBAY.O), doubled on Wednesday in a market debut reminiscent of the 1999 tech bubble. After a highly sought initial public offering, shares in the Dutch company had been priced on Tuesday at 240 euros, the top of their indicated range, suggesting a market capitalization of 7.1 billion euros ($8.5 billion). After the first hour of trade on the Euronext exchange on Wednesday the share price had hit 480.00 euros.