I used to go to both the airport and the east bus station by taxi often. The prices are no where near the same. It would be somewhere between 30-40 for the bus station and 80-100 depending on traffic for the airport. Like Alex said, these places are 18 km apart.

If you aren't short on time though, the cheapest way to get to the airport before 6pm is to take a public bus to the east bus station (like 22 or 29) for 1 to 2 RMB then take the line 6 subway from the east bus station to the airport for 5 RMB.

Your account name 'Luis' seems like a good choice

You could also consider living near the subway line somewhere between Erji lu and New Asia Athletics such that you could get into either downtown or Chenggong within 30 minutes. At present, there is more activity (restaurants, shopping, etc) in this part of Kunming (southwestern Guandu district) compared with Chenggong. Guandu old town is not too far from this area either.

If you go with a Chinese-oriented group, the trip will be less expensive for certain but you will stop several times to buy silly nonsense not related for the destination. Also if you are not Chinese and try to go with these groups you will either not be allowed because of insurance issues (I've been told to go home once after booking with a group to stone forest) or you will get tons of potentially unwanted attention. If you like stopping several times on the way and being asked what country you're from, if you're married, and if you think your country is better than china, etc a dozen times per trip, then maybe Chinese-oriented tours are a good option

If you'll go through the hassle to go all the way down there why not just spend a night or two in laocai or sapa? There are yha hostels over in sapa and tourism in Vietnam for a day or two is similar to china price wise.