Base model prices including destination charges without gas savings discounted.
Tesla Model 3 - $31450 right now after CA + Fed rebate
Tesla Model Y - $48200 likely no rebate available at release
Tesla Model Y premium over 3 = $16,750
Keep in mind the Model Y also includes the premium interior features which cost an additional $3500 to get by upgrading to the Model 3 mid range, bringing the premium over the 3 to $13,250. The Model Y also gets 80 miles of additional range over the base Model 3.