You can sign Harper for 7-10 years at a price tag of $400 million, which I'm pretty sure the Blue Jays would not offer. So in the end, you'll likely end up losing either player since Donaldson won't be come cheap either. So, as far as having a monster in the level of Bryce Harper for two seasons, the Blue Jays have him in Josh Donaldson. I think it's pretty self explanatory, I don't believe I'm way off base here.
Josh Donaldson might be the best positional player to have ever put on a Blue Jays uniform, he's still only 31 years of age. Am I saying he's probably more valuable than Bryce Harper will be over the next 10 seasons? No. Are they currently at roughly the same level of talent, and we should expect this to continue until they both reach free agency? Yes, under reasonable expectations this should be the case.