It could certainly be fine, maybe more than just fine. However, $4 doesn't tell me anything. GPS modules come in different flavors and what you're looking for is the amount of channels it has. A $4 12 channel unit, versus $4 50 channel unit is a huge difference. A 50 channels unit won't be $4. 
Triangulation is a great way to give accurate positioning, assuming you also have good line of sight between all three points. Otherwise you're left with only 2 or worse, just one signal again. However, at the time, it worked. Nowadays, you try to implement that in a metro area and you'll realize really fast that it doesn't work. In came GPS because from above, tall buildings don't look much different than a single floor ranch house.
There are many ways to augment a GPS signal, and lately a lot of companies are using open networks to do that. Google Maps on mobile devices can and does that. You can tell it to use your phone's GPS, or if turned off, it will use whatever open network it can find, including telephone networks. Telephone networks is a great way to triangulate, this is how emergency personnel can pin point where a cell call is coming from. Not only are there powerful repeater antennas covering large areas, but you also have repeater cell towers for say a neighborhood, and when you get down in a city, several tall buildings will also have repeaters on them since the signal can't go through buildings, it just bounces off of them. So the repeaters are used to send the signal out to the taller antennas. Use that in a backwards fashion, and you would be able to locate a cell phone within a block radius. Last time I dialed 911 on my cell phone, the dispatch knew whereabouts I was before I gave her an accurate description of the area (I was on a bike path on the outskirts of town and she mentioned the closest intersection which was a half a mile away.)
But, when was the last time you heard of that network being open to your average Joe? We are in a sense lucky that we have GPS. How accurate it is however, depends on a lot of other things. GPS does nothing for altitude though ... just longitude and latitude. Barometric sensors can help, but that too changes by location as well as the atmosphere.