Just because we have money, doesn't mean we should spend it recklessly and stupidly.
A rich man doesn't stay rich by pissing his money into the wind.
I agree that we need to spend big on a striker, but I don't think we should evaluate all of the aspect of the deal before pulling the trigger. We don't have a sugar daddy like Liverpool, Chelsea and Man City and we don't have United money either, we need to be more sensible in how we spend the money we make ourselves.
What happens if we spend €70m on Higuain, he flops, and we try to sell him on when he's 32? We'll have shat away a load of money with nothing to show for it.
At least with Lacazette, not only will he have more time to come good since he's so much younger, even if he doesn't come good he'll still be young enough that we'll be able to recoup the majority of our losses even if he doesn't reach his potential (just because the market is crazy like that).
Look at Ozil, he didn't start really hitting his stride until his 3rd season here. Same could happen to Higuain, except instead of entering his peak he'll be firmly in decline.