It's not significantly below his value. Suarez is a £50M player who misses a quarter of the season every year with his antics and damages the reputation of any club he belongs to. This reduces his fee to any buyer.
The point about strengthening a rival is fair one - but with £42-45M, and taking into account our recent signings, I think we can improve to a higher level than an Arsenal team with Suarez. It's also worth pointing out that hasn't got many clubs interested in him. If Real don't come in soon, we'll only have had one club interested all summer.
Now Sturridge is here, and Coutinho is blossoming into a world-class number 10, we're not as dependent on him any more, and the money can be put to better use than a want-a-way, stroppy, world-class striker.
Him signing for Real is preferable, but a move to Arsenal should not be dismissed out of hand.