If your client wants a specific reach for a specific price on YouTube, you should use:
TrueView videos ads
The correct answer is:
As an advertiser or ad agency, you can buy placements on a reservation basis–instead of through the AdWords auction–when you want to pay based on the number of impressions (also known as cost-per-thousand impressions) or per day (cost-per-day). Reservation campaigns also let you buy impressions at a fixed rate. Advertising on a reservation basis is best for promoting brand awareness, for instance, if you’re trying to enter a new market, offering a new product or service, or re-branding a product or service.
By targeting your video ads on YouTube and the Display Network, you can advertise to consumers at moments that matter. With a wide variety of targeting methods available to you, such as demographic groups, interests, placements, and remarketing lists, you can reach specific or niche audiences based on who they are, what they’re interested in, and what content they’re viewing.
Read more here: https://support.google.com/partners/answer/2454017?hl=en