
"Particulier" is one of my favorite English/French
faux amis. It means individual. A
cours particulier is a private lesson. A
hotel particulier is a large town house. In English, of course, we've taken "particular" to mean special, or even fussy. It all boils down to the original "particle."
In this case it means "Just for individual customers," as opposed to wholesalers, who presumably are gnashing their teeth to get in.