You don't see a lot of it about. I think it's more expensive than the others generally, but there's more variation in quality.

A lot of people chase the romanticism of "oil on canvas", and they're probably right to, as I think people generally find it "feels more proper" - and the difference might swing it for a sale or exhibition opportunity.

So for example, looking at Jacksons Art Supplies in the UK a 30cm x 30cm aluminium board is £20-£30. That's a flat, uncradled panel - so if you wanted to be able to hang it professionally, it would need either a frame or a split baton or other hanging method bonded onto the panel. Much easier to do that before you paint, of course - as you can fully clamp it together.

You tend to see a lot of photography work printed on di-bond sheet - which is a pair of thin aluminium sheets sandwiching a sort of foam core. You'll see 50 of those for every painting on aluminium - though obviously this depends on what country/city/level of exhibition you're working on/in.

For comparison, a cradled, smoothed wooden board would be about £8 (cradled means it already has a frame for you to screw gallery-quality fittings into).

An uncradled 5mm MDF board, £15 for a pack of 5, so £3 each.

Canvas obviously varies massively - from an art supplier, you may pay £8 to £70 for a 30cm x 30cm Canvas, depending on cotton/linen or fineness of the material.

You can also get 5 for £5 off of Amazon or a craft shop, and most people won't know the difference or care.