Applying for an immigrant visa for a spouse of a US citizen involves a few steps and several fees along the way.
Step 1: Filing the Petition for Alien Relative (I-130) - $420 fee paid to US Department of Homeland Security.
Step 2: Filing the Immigrant Visa (DS-260) - $230, and Affidavit of Support (I-864) - $88 paid online to the Department of State.
Step 3: Medical Exam Fee - Usually between $100-$300, and paid to the clinic where the exam is held. This fee does not include any vaccinations.
If you are interested in applying for an immigrant visa for your spouse, you should consider consulting with an immigration attorney.