There was no explicit trade of stock for tour. The investment by Xerox in Apple happened before such a tour, for entirely separate reasons. There was another Apple exec who was managing pre-IPO external investor interest. There isn't a recorded reason for why Apple chose Xerox (among other investors), if I remember correctly.
However, Steve did leverage the fact that Xerox was an investor to bully the on-site engineers into providing him with the "executive" demo, after receiving the run-of-the-mill public demo and learning that a higher-tier demo existed. It involved a phone call to east coast Xerox Corporate, who instructed the on-site engineers to provide the full demo. The PARC lab director was OOO that day, and later said in an interview that he would have stonewalled Job's request.
Another fun fact, Xerox sold (the majority of?) their stake in Apple almost immediately for a quick turnaround profit post-IPO. Obviously there's no recorded reason for that trade, but my impression is that they didn't think Apple had what it takes to build a proper OS (they envied their ability to cheaply assemble hardware, but viewed their software suite/R&D as a big moat).
Edit: also, Apple engineers were already mid-working on replicating PARC tech at the time of the (not-so-) "fateful" demo. It was behind schedule and not-demoable, and Steve was getting frustrated with these facts. They encouraged Steve to visit PARC to get a preview/demo of what they were building, to ground him to their works' value. There were already a handful of ex-PARC people at Apple for a while, at this point, and PARC's work stems from "The Mother of All Demos" given decades ago. The Alto was unique in its early implementation, but not in its ideas.
However, Steve did leverage the fact that Xerox was an investor to bully the on-site engineers into providing him with the "executive" demo, after receiving the run-of-the-mill public demo and learning that a higher-tier demo existed. It involved a phone call to east coast Xerox Corporate, who instructed the on-site engineers to provide the full demo. The PARC lab director was OOO that day, and later said in an interview that he would have stonewalled Job's request.
Another fun fact, Xerox sold (the majority of?) their stake in Apple almost immediately for a quick turnaround profit post-IPO. Obviously there's no recorded reason for that trade, but my impression is that they didn't think Apple had what it takes to build a proper OS (they envied their ability to cheaply assemble hardware, but viewed their software suite/R&D as a big moat).
Edit: also, Apple engineers were already mid-working on replicating PARC tech at the time of the (not-so-) "fateful" demo. It was behind schedule and not-demoable, and Steve was getting frustrated with these facts. They encouraged Steve to visit PARC to get a preview/demo of what they were building, to ground him to their works' value. There were already a handful of ex-PARC people at Apple for a while, at this point, and PARC's work stems from "The Mother of All Demos" given decades ago. The Alto was unique in its early implementation, but not in its ideas.