Okay, if you're going down that route, most of these costs are fine. But your buying restrictions on some just feel wrong to me.
The idea behind the buy restrictions was partly to emulate the "hard and slow to gain" impact of potion costs. I agree that they're not that well thought out though (though the apothecary one doesn't anti-synergise as much as you suggest, as people don't tend to build an entire strategy around apothecary and copper). Any other suggestions would be welcome.
Thinking about the buy restrictions more:
1) I'm tempted to keep the Curse restriction for Familiar, but drop the discard part, and reduce the price to $4. This permits at least four ways of gaining the card:
a) Opening Curse and $4/$5: unlikely to be worthwhile, but not vastly worse than Potion and $2/$3. If your second buy is a drawer, for example, you've got a reasonable chance of buying a Familiar in rounds 3/4 (4 Coppers and a Curse, 2-3 Coppers 0-1 Curses and a Smithy, etc).
b) Buying a cheap Curse early on, using a spare +Buy: might be worthwhile, but possibly niche.
d) Using a Curse from an opponent's attack: this actually makes Familiar and other Cursers less attractive as opponents become more likely to be able to afford Familiars soon after you start attacking. Though getting a couple of unanswered attacks may justify it.
c) Gaining it some other way: e.g. Remodel an Estate.
It may be that the cost of a) and b) doesn't justify the Familiar. I'll playtest to find out.
2) Likewise, I'll playtest the 'non-Copper in-play' restriction for Apothecary. It's actually a fairly minor restriction (as soon as you have one Apothecary, or a synergetic card such as Warehouse, then you're probably fine) and I'm not sure if Apothecary without Potions would get bought much at $6.
3) I'll try Golem at $7 as I can't think of an appropriate buy restriction.