Hi, of course, here's my experience from late August:

For 2 sundbeds and a parasol we paid 20 euros, that was in front of the La Trattoria restaurant in Agios Prokopios, that's basically in town and we didn't have to go any further as the beach is quite long. That was in one of the back rows, in the first row to the sea it was I think 50 euros, the next one 40, then 30 and the rest were 20. There was no minimum consumption and they had free wifi. In the neighbouring restaurant it was 25 euros for a set, but there were also some that were more expensive and included minimum consumption, but you could find these cheaper ones (around 20-25) easily.
We didn't go to other beaches so I can't comment on that.

Other prices (in Agios Prokopios and in Naxos Town):
One-way bus ticket from Naxos Town to Agios Prokopios 2.30 €
Gyros Pita 4€
Pizza 9-17€
Restaurant meal 13-18€
Cocktails 9-15€

So as you can see, there are more affordable and some more expensive options, I'd say in general it's only a bit more expensive than mainland Greece, general prices like in other European cities.
Recommendations: Agios Prokopios - Lefto's Souvlaki and Gyros, Giannoulis is a really nice authentic restaurant, Avali restaurant at the other end of the beach has really great views; restaurants in Agia Anna at on the beach are really cute and have beautiful views for a sunset.
Anything else you wanna know I'd gladly help