Ideally I would like to spend no more that 250-300€ for a LED that will replace my 400w. I don't need something more than this. I was thinking about getting two 120w of the ones I've attached and spread them so it covers it as much as possible.
And you'll be able to grow cannabis but will you get the results that you're expecting?
If you go with a "brand name" commodity light (Mars, Vipar, etc.) that amount will get a good 2' x 4' light. Migro, based in Dublin, does the "Aray" series that's a great design and you can get a light for a 2' x 4' for about €220.
That's what the market is signaling - to design, manufacture, market, and support a light that will can generate a reasonable amount of light in a 2' x 4' is at least €220 (I'm surprised the price is that low on the Migro, BTW).
For the Migro, the data that's on their product page shows a hang height of 10". While I don't question the accuracy, I do question the validity. Sure, if your canopy is really flat, a hang height of 10" is a usable metric. Here in the real world, very few canopies are so even that you the 1-" figure has any real meaning. For that simple fact, a 10" hang height is not a usable metric for most grows.
Back to your issue - prices represent "signals" - companies offer a product at a given price and, if no one buys, the price is too high. If they sell out "immediately", perhaps the price is too low. The pricing in the grow light market is "signaling" that the price point you're trying to hit cannot be met by the more popular/more commonly sold products in the marketplace.
Either bring more money or change your requirements.
One stragegy is to wait until you have enough funds to light your tent.
Another approach is the incremental approach - don't try to light the entire 4' but to get a light that will do a good job on 2' x 4' of the 4' x 4' and run that light for a few grows. If you find that you like growing cannabis and that you don't kill your plants (some growers don't get the knack of it), then you can either add a second light for the other 2' x 4' of your 4' x 4' or you can replace the 2' x 4' light with a grow light that will cover the entire space.
A 4' x 4' is good sized grow environment. If you go by seed seller data (stop laughing!
) a lot of them are stating that autos will generate about 500 gm/M2. The 4' tent is a bit under 2 M2 so you could be generating quite a bit of cannabis - do you actually want to generate almost a kilo every three months? What would happen if, say, you started with growing just ½ of your tent?
A key point to remember is that with just a 2' x 4' grow space, you can grow a lot of cannabis. Why not start with a light that will do a bang up job on ½ of your tent and then, if you decide that you want more yield, add more plants and a second light?
Hope that helps.