If the Bills think that they can trade up and get a QB that has a good chance of being a franchise QB, then I think they should do it regardless of the cost.
I know that the analytics supposedly say that drafting is a 50/50 proposition at best and that trading away picks has a negative expected return...but, I think that the analysis used in that reasoning misses some important things.
A QB is undoubtedly the most important position in football. A franchise QB gives a team a much MUCH greater chance of winning year after year than a star at any other position.
But it goes further than that. Yes, it is possible to build a contender by having really good players at a ton of positions, but the ability to keep that team intact over the long haul is virtually impossible because then you have a whole bunch of guys looking to get paid. And then you either run into salary cap issues or you have to constantly look to replace those players by either gambling on vets with question marks or by drafting more players at 50/50 returns.
But if you have an elite QB, you pay ONE player a bunch of money and have the luxury of surrounding him with lesser talented guys that he makes up for. An elite QB makes such a huge difference for 10-15 years and gives the franchise much more flexibility and breathing room.
To get that QB, history says that they're generally drafted pretty high in the first round. Talented ones do fall sometimes, but the odds are much lower the lower you get.
So some would say, then just pick a bunch of lower ones and eventually you'll hit on one rather than trade away draft picks.
Only, that's no guarantee either and how much of a waste would it be to keep using draft picks every year on lower odds picks while wasting season after season? Unless your team is terrible, it's very difficult to trade up to get a QB. The Bills have the resources to trade up. There is no guarantee that they will be in a position to draft a QB in the top 5 anytime again in the near future.
All that being said, if they are not fairly certain that the guy they are trading up to get is a franchise QB, then they should sit and wait. Don't get desperate and trade up for a guy that you think is as likely to be Blake Bortles as he is to be Ben Roethlisberger. If you aren't sure, then don't waste the resources. Take Jackson/Mayfield/Allen at 12 or Rudolph at 22 and fill in other gaps.