There is no option to automatically bring in last price paid. I think the closest you can get to that would be to open the previous sales order and then use the Copy button to copy the entire sales order, which you could then edit. If this is a big problem for you, you may want to look an add-on called AltOrder. I don't have any personal experience with it but its features page says "Pricing can  be highly tiered by ‘Customer Group’ or ‘Product Group’, or very specific down to individual customer/item."

Thank you Stephen

A long time ago I wrote a report for a client that charged various unit prices for the same item but with no rhyme or reason.  My report showed, by customer and by item what the unit price was and what the date of that previous order was.  If a custom report might be on your radar for this, please contact me.

Are you using the Customer Mangement page?  If you work off that page you can see all of the sales history.