Like all the other US providers, plans change frequently, very few have unlimited plans, and none that I know of have unlimited-speed unlimited-data tethering plans.
Currently, for $45, the best you can get on T-Mobile is 4GB of unlimited-speed tethered data, and for $70 you can get 512KB/s tethering. The cheapest mostly-unlimited data plan (including fewer limits for tethering) for one line costs $95. Older plans, which had cost less and had less limits, have been mostly phased out.
Another sad irony is to get the cheaper plan, you have to get a credit check, which dents your credit score, just to acquire a "pre-paid" plan. Also, T-Mobile's website seems to have been scrubbed of their prepaid plans, so probably you can only find details via interrogating their salespeople.
Currently, for $45, the best you can get on T-Mobile is 4GB of unlimited-speed tethered data, and for $70 you can get 512KB/s tethering. The cheapest mostly-unlimited data plan (including fewer limits for tethering) for one line costs $95. Older plans, which had cost less and had less limits, have been mostly phased out.
Another sad irony is to get the cheaper plan, you have to get a credit check, which dents your credit score, just to acquire a "pre-paid" plan. Also, T-Mobile's website seems to have been scrubbed of their prepaid plans, so probably you can only find details via interrogating their salespeople.