I've spent more than that in a night, on several occasions. The money certainly adds up if you never check how much you've spent.
I don't anymore! I tanked a few seasons ago and it was similar to spending around £160, in that the hugely positive effects carried through for a couple of seasons. Now I'm still #1 in my league and unbeaten on day 12 in all three cups, but the times I'm a favourite in matches are getting less regular.
In short; don't spend money you can't afford. In a few seasons it'll be like that money was never spent, as your team loses its advantage.