Violation of the law of energy conservation between photosynthesis and respiration?
The Fallacies in the argument

The question contains two main fallacies (some would say sleights of hand) in the energetic comparison of glucose synthesis from CO2 in the Calvin cycle and glucose oxidation via glycolysis, the tricarboxylic acid cycle and the electron transport chain:


  
  The descriptions of the two reactions are incomplete — important co-substrates are ignored.
  The formulation of the question seems to assume that the energetics of a biochemical reaction series is reflected solely in the
  interconversion of ATP and ADP, rather than the free energy changes
  that occur in all associated reactions.
  


Detailed explanation

To make a valid comparison of the thermodynamics of glucose oxidation to CO2 with its synthesis form CO2 we have to consider the single reversible reaction: 

 (The ‘6H’ may appear rather odd, but it is accounted for in the reduction of cofactors etc.. We cannot include oxygen in the equation because it is not involved chemically in the synthesis of glucose. Therefore for this treatment the electron transport chain is not included, although it is discussed later.)

The reaction from left to right is associated with a certain decrease in Gibbs free energy (ΔG) and that from right to left in a corresponding increase of the same value. In a non-biological context this might involve the evolution and use of heat energy, but in the cell it involves the chemical energy of bonds between atoms. We therefore have to consider all the chemical reactions to which the reaction above is coupled, i.e. which receive or transfer free energy. The additional reactions and the free energy changes they involve can be found in the chapters on glycolysis, the tricarboxylic acid cycle and the Calvin cycle in Berg et al. and are (omitting water, hydrogen ions and inorganic phosphate):

From which it can be seen that the chemical energy input required for synthesis is greater than that obtained, contrary to what is asserted in the question

What about the ATP?

Yes, the cell oxidizes NADH and FADH2 and uses the free energy change to build an electrochemical gradient, the dissipation of which generates ATP (30 molecules per glucose molecule is the current estimate). However that is separate process, with no counterpart in the Calvin Cycle, where the NADPH is generated from photosynthetic reduction and not from ATP. However, if you perform a naive ‘currency conversion’ at the rate of 3ATP per NAD(P)H and 2ATP per FADH2, the balance is: input for synthesis 54 ATP, output from oxidation 38 ATP, i.e. the same general result as above.

Popularizing science is not easy, and those who make the effort can be excused for equating energy with ATP (often as clip-art lightening flashes). However if you wish to study metabolism you need to think scientifically about chemical thermodynamics and free energy. The fact that the hydrolysis of ATP to ADP is accompanied by a decrease in Gibbs free energy is not particularly chemically remarkable in the context of the free energy changes of other chemical conversions in the cell (including NAD(P) oxido-reductions). What is remarkable is that the cell has evolved enzyme that catalyse reactions in which the free energy change from this conversion is not lost as  heat, but can be used to offset the +ve ΔG of a reaction to which it is coupled. Reactions involving NAD(P)H do the same thing, but they are limited to reductions, and the free energy change is inconveniently large.

Why the accepted answer to this question is a red herring

The accepted answer addresses a different question to that posed. It cites a calculation of the photon energy required for converting carbon dioxide to glucose. This is irrelevant to the thermodynamics of the Calvin Cycle, which can occur in the dark. It is relevant only to the efficiency of the use of photon energy in phosphorylating ADP and reducing NADP+ (incidentally in an open system) — a distinct reaction. The thermodynamics of the reactions the question refers to — glucose / carbon dioxide interconversion processes — do not involve the generation of their co-substrates.