Artful.ly does not yet offer specific features for Pay-What-You-Want ticketing. But there is a workaround.
When creating an event in Artful.ly, you must set the overall capacity for your venue. Then you have the options to create multiple ticket types with different prices.
Depending on the general scale of your event, you can create a separate ticket type for each price point you'd like to offer as an option. So, if your venue holds 100 people and you'd like to offer tickets at a range of prices, select 100 as your capacity, then create individual ticket types for each price and leave the 'limit' blank. For instance, if you are hosting a small chamber music performance, you might offer tickets at $5, $10, $15, and so on.
Tickets in the Storefront will display from most expensive on top to least expensive on bottom.
Here's an example of what how the pricing will appear in the storefront: