"Ripped off" is really the wrong term for the pricing discrepancy created by having different places to buy the software within one market. The better term is "price discrimination".
Business users of everything are less price sensitive so intelligent sellers of services, software, hardware etc. attempt to capitalize on them through price discrimination.
In this case, Adobe (or distributors) are aware that businesses would rather not have someone shopping around for software when they could be doing something else more productive so they would pay more. The seller is able to capture the surplus. This is a good article that at least early on focuses on inconvenience as the mechanism for price discrimination: https://www.rca.org/page.aspx?pid=2995
Because of the comment before your's, I am not sure whether Adobe is using price discrimination against Australian customers but pharmaceutical companies do price discriminate based on geographic location. (There is also a mention of this in the article above).
Effective price discrimination is a way to extract the correct price from various customers and ignores costs.
If a customer nets value by purchasing a product, the product is priced fairly to them. Different users of the same product get different values, so every seller should try to figure out a way to get price as close to the value gained for each purchase for each customer.
The effect of price discrimination is higher profits for the seller, but it also spreads the cost of R&D more fairly based on value received by buyers. Theoretically PD should drive increased innovation long term.