Groupon

Once the ultimate group discount coupon company. They'd go to a vendor with low marginal additional cost, or just a vendor who was hungry to grow its audience, and agree to put their product on the Groupon "deck," i.e. to market it, basically. The vendor would give Groupon very low pricing per unit in return for Groupon's promise to sell a lot of units.

So a Groupon coupon for, say, a massage (legal, with no happy ending) might retail for $120, with the Groupon giving the buyer a $50 discount, such that their $70 in cash paid for this service just covered the marginal cost of the retailer selling it...but now the massage parlor has a new customer, having "paid" $50 for that customer in a one-time discount. Very clever marketing.

Unfortunately, audiences jaded with mediocre experiences and Groupon's growth stalled then died. No happy endings for its shareholders, at least...yet.