Hi. I’m assuming that you already have a 3D printer. The major cost is the cost of the servos. You need 6 servos. They cost 10-20 EUR each depending on what servo you buy. You also need an Arduino UNO. You can find clones for about 15 EUR. An you also need a roll of ABS or PLA. Normally cost about 30 EUR. Then you need some other parts like fishing line, screws and batteries for the servos. So a realistic budget is somewhere between 120-180 EUR. This budget also assumes that you already have all other tools that you need.