From personal experience as a fitness customer in Hanoi I know how frustrating, daunting and demotivating it is to walk into a gym here and not be given a price list. You know you are being sized up by the sales team with the question "How much are you willing to pay?" and you know how hard it is to walk away and not be hassled to commit to a package.
I personally have had very nice gyms and centres trying to push me into a 4-year package and hand over 60 million VND just to get a reasonable monthly price! Which could be almost acceptable if you were confident you were getting the same price as everyone else, but you are probably not, and who knows if they will still be in Hanoi in 4 years time?!?!