I don't agree with it being a cheap alternative, but the best option. For example, a trip to the airport, checking in, waiting to board and flying out, then repeating that at the other end is a lot more messing around, more time-consuming, and of course more expensive than a quick half-day trip to the border. Just the return trip to the airport, at a good price, would cost me 3000 baht (taxi), and up to 2 hours each way (from Pattaya). Of course, comparisons will vary a lot depending on where the people live.