Professional stock photos are great for websites, blogs, social media or graphic design projects. Stock photo providers allow you to purchase a license to use their photos commercially. The cost of stock photos varies greatly but over the years my favorite has been DepositPhotos. On their website, they have over 100 million stock photos (and vector files).
I pay DepositPhotos $25/month for up to 25 downloads per month. This is under their Flexible Plan. Unused downloads rollover, which is great. The minimum package you can purchase is 10 images for $49. To put things in perspective Getty Images charges $500 for one image.
There are times DepositPhotos does not have an image I need. In that case, I usually visit Photodune (pay per image $5 - $10 ea), 123RF (Similar price structure), Adobe Stock (expensive) or Shutterstock (expensive).
At the end of the day, over 100 million great stock photos to choose from is sufficient for my needs. Their quality is great and I've never had any issues with them. If you're looking for great stock photos I recommend you check out DepositPhotos.