Mathieu Rosinsky is a study in luxury versus gritty contrasts when it comes to his commercial real estate portfolio in Sarasota. On one side, his West Palm Beach–based firm, Belmont Associates, is one of the largest landlords on tony St. Armands Circle. Purchase prices are at an all-time high on the Circle — with some recent deals going for over $1,700 per square foot. Monthly lease rates, following that valuation, are some of the highest of any shopping destination in the region, $150 or $200 per square foot for some stores. Belmont has 10 properties on St. Armands with 17 tenants, and has held property there since the 1990s. The list includes the firm’s most recent purchase: it paid $3.1 million, or $1,631 per square foot, for 361 St. Armands Circle, which houses boutique gift shop Garden Argosy. The purchase, an off-market 1031-exchange, closed Jan. 7. “It’s an A plus plus property,” Rosinsky says.