The second purchase was twice as much as the first purchase, 18.6÷3=6.2, which means that the second purchase cost 62,000 yuan more, and12,000 yuan more.

Because the purchase price is 12 yuan,12000 ÷12 = 1000, that is to say, the first purchase is1000, and the second purchase is 3000. So, I bought 50 yuan for the first time and 62 yuan for the second time.

Earned (80-50) ×1000 = 30,000 yuan for the first time.

Earned (80-62) × 2600+(80 × 0.65-62) × 400 = 46800-4000 = 42800 for the second time.

So I earned more 12800.