Reason for prices to end with a 9 goes back to due to tax rules in the 40s and 50s.

Products less than $100, say $99.99 were taxed lower. A difference of 1 cent pricing made a big difference in tax paid by the sellers. Products less than $10, $9.99 had a different tax treatment. Finishing with a 7 is a recent phenomenon.

Now on pricing a product...think of current alternate choices if the consumer does not buy the product. For example if your product saves 20 hours of work/month, you can say it saves $50* 20 and a fraction of the cost for the life of the event, of even a month justifies the product price. Same can be demonstrated for revenue generating products.