I know nothing about protein skimmers
I know I have made a small DIY skimmer for $44.00 not including pump
If you take the $44 small DIY skimmer, add on a $50 pump, your up to about $100. This assumes that you have all of the tools you need to complete the job. This also assumes that you don't make any mistakes in the construction process. Think about this, what happens if you are not happy with the performance of the skimmer when you get done??
Do yourself a favor, consider a Berlin Turbo for about $180 including pump. For an extra $80, you will save a lot of grief.