'where'=>['Product.sm_price:>'>=4000,'and:Product.sm_price:<'=>7000]
Вот так кашерней:
'where' => ["Product.sm_price between 4000 and 7000"]
'where'=>['Product.sm_price:>'>=4000,'and:Product.sm_price:<'=>7000]
'where' => ["Product.sm_price between 4000 and 7000"]