The drop off might be greater, but there are still good outfielders available.
Rank the following 4 SP/RF combos:
1. Betts and Andrew Cashner
2. Betts and Jason Vargas (or any available SP you like better)
3. Yasiel Puig and Price
4. Domingo Santana and Price
I can see the argument that, given the rest of the Sox team, the last two make for a better overall team. Yes Crazy Puig/ Santana / whoever in RF is a bigger drop off, but the Sox still have Bogaerts, Devers, Martinez, and Benintendi. Those are 4 pretty good anchors...