I'm not sure if the Bitmain Antminer S3+ is that different than the B3. Does one have to buy the power supplies, which seem to be about twice as much as the going rate for the actual machine, or can one find a similar type used for other devices?
Do you mean S3 on highlighted? Are you just trying to compare PSU needed for S3 vs S3+? If I am understand right you will see suggested is very close:
S3:
https://bitmaintech.com/productDetail.htm?pid=00020140630025130637RV8OhOwt06BC - 340 at wall
S3+:
https://www.bitmaintech.com/productDetail.htm?pid=00020140813125800214NBU85kWt0672 355 at wall
So if I understand correct and those are two being compared most PSU's would work for either. At the time then most still ran on ATX psu's but anymore server psu's have kinda taken over.