I dont understand!

[MisterJH]

This is like comparing a $10 bill and a $20 bill.  Sure, they're both useful, but one is MORE useful.

so you'd rather have a 20$ bill than a 20$ bill AND a 10$ bill?

Irrelevant, thats not the argument

[Birdbrain]

It is too relevant. Having 8 cheap burn spells that deal 3 is better than only having 4 cheap burn spells that do 3. At least in a burn deck

[Kagain123]

My 2 cents: take  {Black Lotus} and  {Lion's Eye Diamond}. Which is better? Or  {City of Traitors} and  {Lotus Vale}? How about  {Mox Opal} and  {Mox Diamond}? A lot of factors go into which card is better or worse, mana cost, banned list, current meta etc.

{Glimpse of Nature} is still $20 while  {Beck // Call} is $3 is likely due to DGM just released on 5/3/2013. Glimpse is massively used for legacy Elves. No major tourneys have been run in legacy or modern yet so we can't see what prices will change and where.

[Birdbrain]

Lions eye diamond is better than black lotus. It has more uses at the vary least