There is nothing wrong with your curtains as they are -- beautiful fabric, by the way. But full-width curtains definitely give a calm and luxurious look (see below). Whether you are crazy to spend the money on extending them depends firstly on how much you want the full-width look, and yes well obviously whether you can afford them without causing financial pain. Don't do it just because you think you should to be in line with some stylistic standard.

I think the drapes are fine. I would add some color and accessories. A beautiful chair for your corner. Best wishes!

They are luxurious and perfectly suited to the room's proportions.

keep the curtains, they will go with your chair

Well you could change them at a later time, for now they are fine , at least you have a new idea ready for when you do want to change them.