ClockworkOrange
+SATOR AREPO TENET OPERA ROTAS+
@KonopCh @ClockworkOrange i'm not in europe but i'm in a similar situation. best thing i've found is to do some research about the local distributer of whatever parts you're looking at. you may be surprised to find that you can make some good deals; this is industrial lighting equipment, and there's need for it everywhere. you can also check the bigger electronic supply warehouses like arrow, digikey or mouser, although none of them are the cheapest and none of them is a 'one stop shop' for everything you need.
best option is probably kingbriteled on alibaba (not aliexpress). they just quoted me 250$, incl. 7 day fedex shipping, for a 150w driver and 3x3590+holders+predrilled heatsinks. everything i need except for some cabling, a knob and a frame. could get it together a bit cheaper piece by piece, but this is as close to plug and play as diy gets. if you futz around with it enough you can get the prices down by quite a bit - same if you order big.
The one thing why i dindt try a DIY Led yet is because im frightened to waste my money on something not working, we could argue same can happen with finished product, but i when i checked the price for all components of a hs1 from grownorthern (which i was interested in at that time but couldnt afford) i ended up with like minimun 2/3rd of the sale price- without the knowing if i can bring it together as good as i want it...did your stuuf work out, may even some pix of the plants?