Spoiler for Breaking Bad and Better Call Saul (up to Season 6 Episode 11)
In Breaking Bad Season 2, Walt has produced a lot of Blue Meth in the desert together with Jesse. They get via Saul and Mike in contact with Gus who buys all of what they had produced (before they are hired in the Superlab in Season 3).
When just looking at Breaking Bad, I had the impression that Gus bought the Meth just because he already had the network to sell it and it was quite an amount.
However, in Better Call Saul we learn over the time that Gus has a steady delivery from the cartel (and a growing portion since the Salamancas are slightly losing their share). Also, we know from Breaking Bad Season 3 that Gale has already started cooking by himself with a fair quality (not reaching to that of Walt and Jesse, but maybe even better that the quality of the cartel).
Also, in Better Call Saul Season 6 Episode 10 we learn from Mike that Gus finds Walt and Jesse extremely unprofessional, as he and Saul agree that they Walt and Jesse will not last long in the game. Putting all that together (including Gus being extremely paranoid), I don't get why Gus wants to be anyhow involved with Walt and Jesse (given that he has already a solid company running by his own).
So, question is: What is the motivation for Gus to buy that much Blue Meth from Walt and Jesse in Breaking Bad Season 2?