I've been looking into this
The answer is surprisingly little. You could buy a Gillete 7 o'clock Sterling razor on the 'bay with 11 blades for about a fiver - delivered. Get a tube of Proraso and lather by hand and you've got 2- 3 months' shaves for a tenner.
On the other hand, you could go for "blow the budget" luxury.
1. Razor: a top quality razor will cost £35 - £50 unless you want something exotic or like rose gold
I bought a beautiful Parker Variant for £50
2. Brush. Mine was 9 quid but you could push the boat out and spend £30+ on a lovely synthetic.
https://www.executive-shaving.co.uk/synthetic-vegan-shaving-brushes-at-executive-shaving
3. Bowl. Obviously you don't actually need one, but these are beautiful.
https://www.etsy.com/uk/listing/79548177/shaving-lather-bowl-shave-pot-hand?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=shave bowl&ref=sr_gallery-1-3
4. Soap of some sort. Why not splurge on some saponificio varesino? It's amazing stuff and costs an eye watering 30 quid - but it lasts 6 months of daily shaves. Many wet shavers would count it as the height of luxury to use it every day. As long as you don't buy oils or foams you'd find it hard to spend more than that on soap.
5. Blades - they are practically free. Some people reckon Feather blades are the best - 50 will last you a year and cost 16 quid.
So...luxury option will cost about 50 + 30 + 16 + 2 X 30 + 16 = £172 for your first year - actually a bit less because soap refills are cheaper - say £170. Second year you'll just need soap and blades so it will cost about £75.
Meanwhile a Cornerstone subscription (and remember this a "cheap" alternative to buying cartridges in Boots) is £14 for 6 blades and a bottle of King of Shaves serum will cost about £6 for 6 weeks' supply. I make that very close to £175 a year. Every year.