It would mean 2 FFL transfers, as my local FFL (East County Guns in Elma, WA) will accept a long arm from a non-ffl as long as the sender includes a copy of their drivers license. He charges me $20 for transfers. I would do the work, and then ship it back to your FFL, who would transfer it to you for whatever they charge.
If you end up buying one on-line you could have it shipped directly to East County Guns and save a little bit.
So all told probably looking at around 75 for shipping and FFL fee's.
And another 75 or so for the parts (Have to be US made, so I would recomend a Tapco G2 double hook, US pistol grip, US buttstock, and either a US gas piston or front stock).
I have not done a Saiga shotgun conversion, my Saiga being a .308.