If you're like me---I always need something concrete to give me a good handle on things---this may help put the amount in context. Remember Catherine's 10 guineas is equal to 210 shillings (as Graciela has stated, each guinea being 21 shillings) The years may vary a bit from NA but I found it helpful nevertheless.

From the novels:

*The Moor Park apricot tree that Mrs. Norris speaks of cost 7 shillings (6)
*To hire Repton to make improvements to Southerton in MP cost 5 guineas a day (6)
*Henry paid 5 shillings a yard for true fine Muslin for his sister, apparently a bargain (3)

In real life:

*While living at Chawton Jane Austen had a Grey Woollen Cloak made up for 10 shillings in 1812 (letter 29-30)
*"It was also in 5 December 1794 Mr Austen paid 12 shillings for a 'a small Mahogany Writing Desk with a Long Drawer and Glass Ink Stand Compleat'..." Janet Todd