Split from this thread so as to not take the EW thread way off track.
We've restricted Golem and Chalice, and Shops are still the best deck. The problem isn't just Workshop. It's the fact that Wizards continues to print insane new cards. This year we got Vehicles and Eldrazi. Last year Hangerback. There is no end in sight.
The new prison cards that are sometimes perceived to be too good are often well priced or even too expensive for the formats for which they are printed. WotC is not going nerf artifacts from now until the end of time just to prevent one deck in the smallest sanctioned format from being too powerful. While Workshop may not be the problem, it is a portion of the problem that WotC can address without negatively impacting their more profitable formats.
Balancing costs on all cards is a fascinating discussion. The simplest parts are quite easy. For example (5) is easier than UUUUU, which is easier than WUBRG. It gets more complex when we compare something like, say, 3UU vs 5U. Unfortunately, artifacts are more difficult. Their primarily-colorless nature means that, outside of something in the card's text box, the only ways to make an artifact harder to cast are to increase the cost or to require <> rather than (1). That second restriction has no effect on Workshop.
Lands are "intended" to produce approximately one mana per use. Workshop produce thrice that. The only other land that matches that efficiency and is relevant to Vintage* is the restricted Tolarian Academy. Effectively, lands that produce >1 mana act as one-sided cost reducers in a deck full of two-sided cost increasers.
Most "cost reducing" lands have some drawback. Eldrazi Temple only reduces costs for Eldrazi. Gaea's Cradle only reduces costs if you're playing a creature deck. Ancient Tomb costs life. While Workshop does have a drawback, that drawback primarily functions to place Workshop in a deck where that drawback is all but non-existent. While most cost reducers are indeed played only in decks where their drawbacks are minimized, they are never minimized to near-zero. For example, a turn one Gaea's Cradle does nothing without one of the few, usually bad, zero mana creatures. Whereas all a Workshop needs to be good in your opening seven is to not have drawn one of the worst possible hands for you.
In a world where cards have no history or cost, I think a Workshop restriction is not only obvious but has been so for quite some time. However, as we do not live in that world, we will likely instead have several Shops cards sacrificed at the altar of not restricting an eight hundred dollar four-of.
I could certainly be talked into an Ancient Tomb restriction. While I don't think it would nerf Workshops to the point of not top-8ing, it might encourage people to build my second deck ever and my first Vintage deck, 5C Staxx.
A new card of Grafdigger's Cage-accessibility preventing all mana taxing would be a nice shakeup.
I'd love to discuss how this card might be written. I'm thinking something along the lines of
Cost reducing effects controlled by other players are not applied to cards you own.
This would allow Trinisphere to continue to function, so Workshop isn't 1000% hampered. Alternatively:
Cards you own may be cast for their casting cost.
Would put you in the same clause as Trinisphere. The text however, looks really dumb.