I don't understand how they could price it at $249 without knowing what happened. Since they haven't looked at it, at least going by your description of events, it sounds like this might be something they are real familiar with, as in a recurring problem with this particular combination of sink, counter top, and installation crew.

I would be hesitant to have them out again without some independent knowledge of what is going on. Is there a friend or relative you can call to take a look at it? Someone with least a handyman's level of expertise.

This issue has arisen before. Read the link, especially MightyAnvil's clear explanation of correct installation.

I would pay nothing until the cause was clearly determined. If they used clips, glue and followed the manufacturer's instructions but the sink broke away due to a weak or disintegrating counter or supports, then you owe them. If they did NOT follow correct installation procedures, then they are at fault and should install it correctly.

And, although others may disagree, I believe that a correct installation should certainly not budge (much less fall down) if one plops a 30-pound item into it -- no matter whether that item is a frozen turkey or a climbing child. Read the sink warranty carefully, I expect you may find in small print that there is a weight-limit warning -- and that the weight limit is dependent upon following the manufacturer's installation instructions.

Here is a link that might be useful: Undermounted sinks fall

Since they are not covering under warranty I would not have the same installers back to repair it. I would call someone else since it was not installed properly in the first place, sounds like the first installers didn't know what they were doing.

I'm with Grayce: your installer is a crook, and you aren't under warranty, so find someone better to do the repair.

I feigned ignorance of the issue, asked different stone yards how the sinks were attached as a litmus test-- if they didn't use clips, I wouldn't consider that yard. All of the ones I spoke to clipped, so it wasn't ueseful in that reguard, but it freed me up to choose based on stone [and price, of course...]

Silicone is not a structural adhesive. There needs to be something mechanical holding the sink in or it needs to be properly bonded for the solid surface types. I agree with everybody else, if you're going to have to pay for it, get someone with a clue.