If you are in coach mode it will be cheaper for you because the CPU has to carry Signing Bonuses (as the owner) and the tap is open with the CPU.
Most High overall QB’s in Madden 20 are asking for 266 mill or at least over 200 mill. If you try and afford that you will end up only having QB after 3 years. This may sound very scary to you but you will let him go to Free Agency in the Free Agency Signing Period in the offseason. If you are not in a league by yourself (Solo) then you want to be very careful but not freaked out and give more then you should. Remember there are always back up plans, you will be able to recover regardless.
To sign the hefty beast of a whale you will want to offer him almost all of his money in Signing Bonus, which is guaranteed money. If he asks for 5 years then that is preferred as you will save money over time. Years to a player at this overall don’t mean as much unless he is regressing.
Offer him 550k salary and let’s say he wants 266 mill, offer him 20 mill Signing Bonus which is 144 mill with 140 mill guaranteed at a 7-year deal. That will give you roughly 60 points, and players want Signing Bonuses much more than they want salary, so they will not be able to match points with you without spending a fortune. If you have to add a little salary to it then do it lightly, however never spend more than 160 mill.
If they are not a 99 overall yet than you will probably only have to spend a little over a 110 million for them.