“Charity” shops in my area are for profit businesses. Sure someone is getting a small donation, but their board members pull large salaries. Never mind their free inventory and usually underpaid labor.
The directors getting paid doesn't make a charity for-profit - that's dependent on what they do with the remaining money after paying salaries. For-profit businesses distribute surplus (i.e. profit) to shareholders.
It's a common complaint that donations should not be used to pay salaries, but the important question should be how much leverage those paid staff can extract out your donation. Skilled people usually don't want to work for free, but they can magnify a donation by reaching more potential donors via advertising, more appealing shops, etc.
Legally you are of course right, but there are certainly charity shops out there which are exploitative and even designed to enrich their owners. One well-known example is Humana People to People which is run by something probably best characterised as a person-worshipping political cult (Tvind).
It's a common complaint that donations should not be used to pay salaries, but the important question should be how much leverage those paid staff can extract out your donation. Skilled people usually don't want to work for free, but they can magnify a donation by reaching more potential donors via advertising, more appealing shops, etc.