Maybe in some places, but the competition in the US is a joke. You either go with a decent plan but terrible service (Sprint), or you go with good service with virtually no control over your use (Verizon/AT&T).
Are you for real? It's easy. Look at prices and services from all major carriers in the US over the past 5 years. the prices are going down and you're getting more for less. It's a tough back and forth and every month or two they try to one up each other. So that's how prices are going down.
What you got in a different market doesn't matter. It's inarguable that prices are going down and it's inarguable that there is no monopoly. There isn't even a duopoly. What is arguable is that you should perhaps get more for what you pay. But the velocity is still down, even if it's not yet as low as it should be.
Original plans were unlimited 3g data. All t-mobile high speed data plans automatically included unlimited low speed data if you go over. They also have an unlimited 4g lte plan that's only $30 more than the basic 1gb plan. And they currently have a special offers to for 2 lines w/ unlimited data.
I had the original unlimited 3g data plan with AT&T. That also required paying $20 a month to get unlimited texts. I think I paid $10 a month for 250 monthly texts because that's all I needed. That was the height of mobile pricing bullshit in my eyes.
In South-East Asia, you often get a prepaid contract including 5 GB for between $5 and $20. This is 10x cheaper. Sure, salaries are lower, but the equipment is the same.