I have noticed that the pricing in Buenos Aires is in flux. Services are very inexpensive, while products are not. A single pair of mens sports socks was $2, a can of tennis balls $8!! But transit is unbelievably cheap at about 25 cents for a local bus trip (it is subsidized by the government, get a SUBE Card).
Other services: string tennis raquet for $5US labor. Massage $20US.
But a pair of plastic flip flops were $7US!! In Canada you could get them for a few bucks.
That's Judy assisting me with the litre of Biro!! She had a pizza for lunch.