@LordWooFakFak64:
First of all, CDP has ~20 years of experience as a publisher/distributor, so one would think they know how the business works.
Having a budget for marketing larger than the budget for production is nothing new nor uncommon in games industry or elsewhere. You may think that it's about diverting resources from production (ergo the game will be less than it might've been), but the bottom line is what's most important in the business. There will be no resources to spend on the production should the income not be sufficient. Bigger production budgets are possible only when the company's income is also bigger, and sadly a good product does not usually sell well by itself.
Plus I find it likely that at least some part of the marketing budget will cover various kinds of merchandise, which could bring some additional profit.
And, there is no single piggy bank where all the money is, both for production and marketing. As Guy said, marketing will be up to distributors, with them financing it, and only then it will be deducted from CDPR's income. So it's not as if CDPR is diverting any money from production.
As for lets plays, I think you overestimate their reach. It's all well that you check them before making a purchase, but you're a bit too small a sample to be called representative. TW2 had quite a lot of lets play videos, and had some exposure on the most prominent Youtube gaming channels, but it's still easy to find people who've never even heard of TW. (Well, at least it was easy few months back
) So I wouldn't overestimate the influence of such communication channels where broad audience is considered.
And I want to point out the fact that even though the game is being developed in Poland, which implies lower production costs, the marketing is targeted worldwide, so the budget must include higher work and material costs, like the ones expected in Western Europe or North America.