I would. Prime 1's amazing.
Besides, aren't the NPC! titles sold at the full price of new games in Europe? So, you could buy Prime 1 for 50 Euros, and Prime 2 for 50 Euros, or you could get all three on one disc for the same price. I don't see what there is to complain about.
And even if they are going for 30 or 40, that's still a good deal right there.
Plus, of course, about 48.5 million Wii owners didn't, you know, get Prime 3 - and a comparable amount missed out on the first two as well. Nintendo did say they were releasing the NPC! titles so that their GameCube classics that didn't sell so well can reach a broader audience...