Hi, my name is ***** ***** I have been in the home improvement and repair field for 20 years. I will be very glad to help you today. The bottom oven igniter is likely not getting voltage because it has failed. When the igniter is activated it opens the gas valve. If the igniter is not activated then the gas valve for the oven will not turn on. If you have a multi-meter you would check that the igniter is getting voltage and also check the continuity. If you are unfamiliar with checking voltages then replace the igniter and all will be well.
No it should not be a costly fix at all. About 30 minutes of the repair person's time.