I think cheaper is better

Remember most Web2 games thrive on Microtransactions...

That's only $.10... That's only $.75...

This is what appeals to the masses... this is what most people can afford...

I like this idea for sure!

Edit: You might also consider throwing in a "Jackpot" chance for Epics and Legendaries...

If you have a 2% Chance in a normal pack to be a Legendary... and that pack is 4,000 DEC...

Having a .2% Chance in a 1,000 DEC pack isn't going to hurt the values of Legendary Cards... but... the power of that "Lottery Draw" is HUGE.