  Column density ratios of complex organic molecules are generally constant
across protostellar systems with some low-level scatter. However, the scatter
in formamide (NH$_2$CHO) to methanol (CH$_3$OH) column density ratio is one of
the highest. This larger scatter is sometimes interpreted as evidence of
gas-phase formation of NH$_2$CHO. In this work we propose an alternative
interpretation in which this scatter is produced by differences in the snowline
locations related to differences in binding energies of these species and the
small-scale structure of the envelope and the disk system. We also include
CH$_3$CN in our work as a control molecule which has a similar binding energy
to CH$_3$OH. We use radiative transfer models to calculate the emission from
these species in protostellar systems with and without disks. The abundances of
these species are parameterized in our models. Then we fit the calculated
emission lines to find the column densities as done in real observations. We
find a correction factor of ~10 to be multiplied by gas-phase
$N_{NH_2CHO}/N_{CH_3OH}$ to give the true abundance ratio of these two species
in the ices. We find that models with different physical parameters produce a
scatter in $N_{NH_2CHO}/N_{CH_3OH}$, comparable with that of observations. The
scatter in $N_{NH_2CHO}/N_{CH_3OH}$ is larger than that of
$N_{CH_3CN}/N_{CH_3OH}$ in models consistent with the observations. We show
that the scatter in $N_{NH_2CHO}/N_{CH_3OH}$ will be lower if we correct for
the difference in sublimation temperatures of these two species in observations
of ~40 protostellar systems with ALMA. The scatter in $N_{NH_2CHO}/N_{CH_3OH}$
can be partially explained by the difference in their binding energies. We
conclude that gas-phase chemistry routes for NH$_2$CHO are not necessary to
explain the larger scatter of $N_{NH_2CHO}/N_{CH_3OH}$ compared with other
ratios.
