On the other hand, in terms of discovering what users will pay for Creately, the experiment was a failure. By essentially structuring the system as "donate us money", you prime the users to think "Hmm, even $1 is being generous to them. I'm a big spender... I'll go as high as $3." That is, ahem, an insane price point for any service.
You have to convince someone to dig out their credit card to pay you money. There is essentially no differentiation between $3 and $9 at that point, since neither amount is an appreciable amount of money to working professionals. (Students are another case. Since they're going to complain long and loudly about being made to pay, and are going to do their level best to steal your service anyhow, I think you can quite rationally make the decision just not seek their custom. Alternatively, you can segment your plans such that one which is free but helps your marketing meets their needs.) There are tremendous advantages to the business, however, from moving from $3 to $9. (Revenues net of Paypal fees just increased by a factor of four.)
Note that $9 is still VERY VERY cheap. The fully loaded cost of a professional exceeds that for every ten minutes. Also, if you look at any SAAS business they'll tend to tell you the same thing: the most expensive plan, which is typically bought by employed professionals spending other people's money, brings in more revenue than any other plan. This has been mentioned by Wufoo in interviews, it was true of DropSend when they published their numbers, and I know it to be true of three other companies who have not given me explicit permission to make the fact known.
Additionally, as Creately noticed, the kind of people who are attracted by "This only costs a buck!" are the worst customers in the known universe. They cause hugely disproportionate loads on your support resources, and feel entitled to do so because they're Paying Good Money For This, Damn It. They tend to churn like crazy. They'll fail at the most trivial of tasks (like typing in their credit card details) and then blame you for it. (When you spend a buck on something, if something goes wrong it is the merchants fault, the lazy bum. When you spend hundreds on something, you darn well check to make sure it went through alright.)