Shoppers come from Duvall, Dupont and Des Moines to shop at the Mercer Island Thrift Shop, which has proved to be a gold mine for the City of Mercer Island.

The store, which originally began in 1975 as a rummage sale to benefit Youth and Family Services, has thrived, bringing in an average profit of $500,000 each year since 2007. For the most recent 12 months ending in May, the store grossed $985,000. According to figures from the city, the store’s profit margin has been at or above 59 percent each year, with the margin in 2011 at 68 percent.

All funds are put toward paying for the City of Mercer Island’s Youth & Family Services department.

The store relies largely on volunteers to operate the shop. The city employs one regular full-time, exempt employee and two contract employees to manage the store. According to Suzanne Philen, the city’s coordinator for the shop, the store had 140 volunteers involved with the shop this past year. About 60 to 65 are who she calls her “core” volunteers.

Volunteers include retired Island residents as well as students from Island schools, and Bellevue College, earning public service credits or part time pay.

Over the past four years, shoppers have been asked their ZIP code when they check out. The data indicate that shoppers come from places as far away as Bainbridge Island, Vashon Island, Lynnwood and Federal Way.

And just which shoppers spend the most at the store that sells high-end castoffs from Island residents?

Well, Islanders do.

Islanders alone spent $620,000 at the store during the 12 months ending this past May — roughly $75 per household; a whopping one-third increase over the amount spent during the 12 months ending in May of 2008.

Interest in the thrift store from surrounding communities has increased over time as well. Shoppers from Bellevue ZIP codes more than doubled their spending from $34,000 in 2008 to more than $86,000 over the past twelve months. Shoppers from the combined zip codes within the City of Seattle spent $40,000 for the 12 months ending in May of 2008. That amount jumped to $101,000 for the12 months ending this past May. Shoppers traveling to Mercer Island to shop from the cities of Renton and Kent spend $11,000 and $3,000 respectively for the 2007-2008 period. Those amounts increased to $24,000 and $12,000 for the 12 months ending this past May.

A family from Marysville at the store recently told Philen that they make the long trip to Mercer Island to shop because, “this is the most terrific thrift store around.”