I got curious and looked up the relevant sense of "boutique" in the Oxford English Dictionary lol citations
[h=3]1. Characteristic of or likened to the type of goods sold in boutiques; spec. designating a product or service offered by a small, exclusive, or specialized business; (hence more generally) exclusive, highly specialized, appealing to connoisseurs.[/h]
1964 N.Y. Times 27 May 4 (advt.) Dusky linen-like spun rayon—..very boutique with just the right touch of embroidered yarn.
1978 Washington Post 22 June (Maryland section) 7 (advt.) The newest and largest selection of California boutique wines in Montgomery County.
1993 Institutional Investor Sept. (Advt. Suppl.) 9/2 Its [sc. the bank's] small size, high profitability and exclusiveness enable it to provide boutique services.
1996 N.Y. Rev. Bks. 19 Sept. 6/4 But they are also all boutique movies—imports, personal projects, film festival fare.
2000 What Mountain Bike Winter 81/3 The rest of the kit is decent light gear from house brand Bontrager but you could get the bike down below 21lb with a bit of boutique upgrading.