Honestly it's getting out of hand, Blink dagger is by and far the most powerful item in DoTA, so powerful in fact that the only time Blink Dagger is an outright bad purchase, is if the hero in question already has blink built into their kit, ALL other heroes can utilize Blink to a lesser or greater extent.
It's not uncommon to see 3+ Blink daggers on one team alone, with the incredible range of that item you can surprise buttsex anyone you want, constantly.
It's especially strong for these unstoppable kill combos like Tiny, LC, Lina with Eul's etc. bringing back the 75 mana cost would at least leave blink dagger's undeniable initiate and ganking power, but would make it so you need to be more careful about usage, and/or getting mana alternatives to keep up with it, rather than lulz spam on cooldown.
I seem to be in a minority here, with most people enjoying the 9 min rush to blink only to completely stomp afterwards giving your enemies little to no counter play.
*Alternatively* implement an item, costs 2250 gold, gives you 2+ to all stats, and has a 1250 range aura that deals 1 damage and heals 1 damage per second, name the item "Fuck you blink." kkthx.