I'm thinking of it from the customer's perspective, not the manufacturer's.Depends on the influencer. For example sending a the new models computers to a influencer that will get 20-30k views on a review video might be worth it. That might be a lot of exposure in their target market for $1k in cost.
Turning it around, sure, if the added cost to me as buyer is minimal and the pros who tell me why they got what they got is helpful to me, then it makes sense.
(And I'm the first to acknowledge hypocrisy on this: I want the discount for myself, but don't want to pay for it for others!)