If a team wants to obtain five extra wins they can cheat, pray that one materializes within their farm system, trade for them, they can acquire them through free agency. The latter two categories are the only two options that will be legitimately available for most teams, and each is dictated by the market value of the players involved. Even if you are obtaining players through trade that are under team control and thus are being paid far less than the value they create on the field, the price you will have to pay through trade will be dictated by their surplus value which is again tied to that same $/WAR figure. 70 grade position prospects produce around 12-13 WAR on average so they are valued at around $110M. If you want to trade for one then you need to find $100M+ surplus value of your own to make the deal work.
https://blogs.fangraphs.com/an-update-to-prospect-valuation/