What’s the appeal? We’re not talking Fruit of the Loom here, folks. Boxer Bay caters primarily to Yuppie gents who jockey for status in $100 silk boxer shorts by Hanro of Switzerland or $68 cotton knits from John Smedley of London. The Boxer Bay inventory also includes $400 silk robes by Fernando Sanchez, $550 Hanro pajamas and $35 Bali batik boxers. Hillis expects the Los Angeles shop to gross $36,000 in June - and as much as $500,000 in 1991. That may not be farfetched, considering some of her customers’ spending habits. Last week a man in the Los Angeles outlet told the manager, “I’ll take everything,” and in less than an hour bought $2,400 worth of undies and other personal items. Now that’s inconspicuous consumption.