Club1 Hotels is a membership site, and that lets them sell rooms at a discount, offering lower rates to consumers instead of taking their booking commission. They report that they make money on membership fees rather than individual bookings. (Since they’re a membership site hotel best rate guarantees for direct booking on a hotel chain’s website don’t apply.)
Their membership normally costs $675 for a year, but they’re giving away one year memberships that provide access to discounts (but don’t come with a Priority Pass for airport lounge access) now. It’s worth signing up just to check out pricing. I’ve seen plenty of hotels where you can save hundreds of dollars through the site, though you may give up hotel loyalty points booking with them.