If you're frugal like me, you can rebuild your starter with a new brush plate and clean it out. It's a build up of grease, dust and carbon that stops the starter from working. It's not actually shot, it's just dirty.
The hardest part is getting to the thing, you have to take out the intake bits and then you can get to it to remove it. Fixing it/cleaning it on the bench is a piece of cake. It's half a day and £15 to DIY, vs Much less effort but probably about £300 to have an indy swap in a new one.