I'm normally the Macgyver type, but when I decided to try SIPs, I bought myself out of the chore of building my own. Bought 10 black buckets and 10 SIP inserts. Cost me about $200, so $20 per assembled unit. Didn't have to track down parts or spend time building anything. Everything was shipped straight to my door. For me, the convenience was worth it.
can you buy the sips insert and supply your own bucket ? lots of times local dollar stores have black five gal buckets for cheap.
i normally diy myself. sometimes it's not worth the bother.