I'm wondering if anybody else has experience writing their own Sefer Torah, how long it took them and how much it cost.
It took me about 9 years and about $3,500 to write mine.
It took me just over three years for each that I did. I wrote roughly half an amud(21 lines a day) using a reed. The cost was just over $8k, but I used an exceptionally high quality klaf(better surfaced and no gid marks). For the second it was just over $12K(though that was a nightmare of a sefer to write). I wrote in Klaf Gvil, which costs double the price and then you have coat it with a special substance to keep the letters from falling off, unless you want to dig up a really old recipe for ink and brew it yourself.
Most professional sofrim can write one in under a year. However at the same time they write full time and have special gadgets to help them along.