Yeh it may seem a little pricey but as Noodleman said, its only £5million upfront. And I don't think thats overpriced for a hot ENGLISH prospect for the future, especially at a club like Arsenal which needs some more englishmen.
If you think about it, if we didn't buy theo then the likes of Chelsea would have bought him for a much higher price. Look at Wayne Rooney, 18 years old and Man u buy him for £30 million.