Just like anywhere you can reduce your costs if you take the time and trouble to search for the best prices. It's possible to reduce food
and drink bills by half and still eat very well in France
in Leader Price
, Lidl and Aldi & Spain
by Dia, Lidl, Aldi plus of course the weekly street markets, most towns have an everyday till noon indoor market Le Halle (France) Mercado(Spain).
Caves (Carve) in France
sell wine from a petrol type pump so take your own empty plastic water
bottles for refilling with wine. Some supermarkets sell from the barrel in Spain
supplies can also be kept low by thinking 'out of the box', some spares can be bought cheaper in the UK off e-bay, Allpa in Nijmegen,Holland & SVB24 in Germany
either delivered free or shipped down via low cost carriers.
I recommend Sendmybag.com for low cost parcels, packages worldwide.
I hope this is helpful to you, safe cruising.