I attend MGH IHP's OTD program and they gave me a good scholarship that made tuition cheaper than any MOT programs i applied to (factoring in cost of living as well).
So, if you want to go to the cheapest program, you can apply to inexpensive MOT programs, but don't rule out newer OTD programs. They are more eager to attract students (and in general less people apply), so the chances of getting a good scholarship are much higher.
As far as why I applied, yes scholarship opportunities was a big one, also MGH hospital is top in the country and the partners network is excellent as well, so we have great FW connections. I also would like to teach one day and I think an OTD will be beneficial. Also, yes the program is longer, but the curriculum is very thorough and we cover more populations in more detail than a typical MOT program. The faculty and students impressed me on interview day and that sealed the deal.
Another pro since starting, the workload is very manageable which makes a p/t side job totally possible and further reduces cost of school.