Vendor bought sampire suit will be 40-80mil and it might not be optimal because it usually doesn't take into account:
1) despicable quiver or jumu's sacred hide fire resistances
2) earring of protection
3) armor refinements
4) imbuing 5% HCI vs 5% DCI depending on the clothes/accessories you are wearing.
5) because of #1 and #2, vendor bought suits will often waste another imbue slot on resist. For my suit, I only had to imbue resist on one piece while maintaining 75/100/70/70/75 resist. I notice vendor bought suits imbue resist on two-three pieces just to get you to 70/95/70s.
If you have time and are comfortable with spreadsheets/excel, I would 100% make the suit. It is way cheaper and more optimal. My first suit took 4+ hours to make though plus another 4 or so hours of prep work and reading. (I was a complete noob 3 months ago so I had to learn from scratch) Buying/farming all the necessary ingredients to craft/imbue/enhance takes time. I highly recommend just buying the ingredients.
Rough estimate cost to build my own suit: 5 charges forge tool (17.5mil) All imbuing ingredients will run you about 500-800k per piece. Another 250k per piece for Powder of Fortifying. Maybe another 1mil for reforging tools.