Hola, José, All the changes you indicate would convey the same essential meaning. Used to merely stresses the habitual or ongoing past activity. Often (as perhaps here) the writer has varied the verb form for stylistic interest and clarity-- the shops sold products every day (ongoing past activity); 'you' purchased on occasion (as individual past events).
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.