First, as far as I know, Hobby Lobby is not asking for the right to not pay for contraceptives on the basis of wanting to save money. They’re asking for the right to not pay for contraceptives because they’re religiously opposed to contraceptives.
Right?

On that point alone, the cost of contraceptive coverage is completely beside the point.

Further, this specific claim misses some rather significant facts under the current law.
Like I said, I don’t know what they pay for insurance, but a Weekly Standard article (yesterday, I believe) tells us that the ACA will penalize an employer $36,500/yr if they provide employees with a non-compliant insurance plan. (An insurance plan that does not include “free” contraception would automatically be non-compliant.) The article didn’t specify if that’s per employee, or for up to a certain number of employees, but that doesn’t really matter for this discussion. The point is that if Hobby Lobby provides insurance that doesn’t cover contraceptives, the company will be financially penalized.
So if we're going to talk about the cost, we have to accept that under the law as currently defended by the government, insurance that does not include contraceptives is more expensive than insurance that does (assuming everything else remains constant and the policy is otherwise compliant).
The cost of the policy itself makes no difference.

The argument at hand is: Under the current law, Hobby Lobby will be forced to provide coverage they object to on religious grounds. If they fail to comply, they will be penalized. They want relief from that penalty on the basis of religious freedom.

As a side note (not directed at you, firehawk), opponents of Hobby Lobby need to do a better job of coordinating their attacks. It seems to me that this assertion (that contraceptives cost absolutely nothing) kind of knocks down the alternative attack that this is all just about greedy corporations trying to increase profits for the 1%, doesn’t it? (I saw both arguments on the board yesterday.)