PCIe 3.0 on a 2.0 motherboard

[#1]

In looking for a new build time and again on sites I am noting that builds are offered with PCIe 3.0 graphics cards on motherboards with PCIe 2.0 and I wonder; is it not a waste of money to pay for a PCIe 3.0 graphics card if the motherboard will only allow it to function at PCIe 2.0?

[#2]

It won't be a complete waste as it will still give a performance boost however on the other hand it will be throttled and not get the full usage out of the system. You could always look at upgrading to a cheap motherboard which supports PCI-E 3.0 x16 or save up abit longer to get both

[#3]

Are there many (if any) PCI-E graphics cards that can actually make use of more than the PCI-E 2.0 bandwidth?

[#4]

Seems many, if not most of the latest graphics cards are PCIe 3 (at least the ones I'm looking at - AMD), but whether they can indeed make use of the bandwidth, I don't know - especially when I don't understand the complexities of it all. Well anyway, nice to know that there would still be some worth in it.