VRT is required for validating the User Interface of the application. It targets the overall Look and Feel of the aplication including CSS, HTML, Quality and type of images, alignment & positioning of the various fields and user controls, Style Guide etc.
In today's competitive world when there are lost of similar web applications (eLearning), one has to come up with certain features different from other applications it can be Content, Accessibility, Cost and User Interface (ofcourse). UI is the first thing which will catch an user's attraction, so this must be validated. Again, this testing becomes utmost important if your application if supporting Multiple Browsers and Mobile platforms and that too with multiple resolutions & most important different mind set of peoples (I think, there is no reason in current times of not providing support to these features). It is also required if you want your application to be responsive.
As per me, competition is more when it comes to startups as they have to grow and for growth they need to work and deliver extra set of features and improvements. But, if your application is already live and you have already received a good user response then priority of this testing can be reduced. Ofcourse, with the delivery of new features and use of new technologies you have to maintain and nurture the Quality of the product (both in functional and non-functional ways) to avoid broken CSS and Style guide with new features, as breaking CSS is easy, but testing it is hard.
I have worked in a project where competition was there between different applications of the same client for achieving highest rating for both Functional and Non-Functional features (like GUI, Performance, Security etc.). So client has 2 members of special team for validating only the UI of the application across different browsers (thank god we didn't have mobile support at that time).
There are many tools (free and licensed) available in market for VRT. But as mentioned by experts in earlier post of SQA that biggest & most efficient tool for validating the visual appearance of a web application is Human eye and brain. So, you can go for manual testing too, but your problem becomes more bigger when you added 'No QA team' is there for carry this kind of testing either manual or automated.
If I have been in your place, I will talk to the third party that after 1 month of free trial, I (including other team members) will analyze their findings & reports and if we find that they are adding some good values to my application, then we can continue with them, else terminate the contract. Another option, is to hire a QA for this activity (obviously not only for VRT but also for functional testing too, if feasible). This will be more efficient and good paying option in long run.
Courtesy to the existing post.