We present a simple analysis of the carrier contribution to the elastic constants in ultrathin films of Bi under magnetic quantization in accordance with McClure- Choi, Cohen, Abrikosov, Lax and parabolic ellipsoidal band models in the presence of spin, broadening and temperature respectively. It appears that the said contribution increases with increasing electron concentration and decreasing film thickness in various manners. The McClure and Choi model shows this more significantly than other models. We have also suggested an experimental method of determining the said contribution in degenerate materials having arbitrary dispersion laws.