For reference, I have a travel blog, and I would love to make money from it someday (just starting the process of changing it from a "friends and family" blog to a more business-like one!) but I am not yet even close to being an influencer, and definitely no expert on this. I have been learning about the travel blogger industry, and in general, I think even most travel bloggers would look down on this offer. It's people like this that make it hard for other bloggers who can offer value.
Firstly, asking for any more than two nights of comped accommodation is seen as being a bit greedy. Any good blogger should be able to make an assessment of the property/service in that time. If you want to stay longer, pay for it. Most people will also not ask for meals to be included, but sometimes they are offered by the property as another way to promote it. I also tend to agree the reach of 500k only on instagram is, well, not ideal for this sort of offer. By the time the stay is over these posts will have faded into history. A good travel blogger will have a website and a SEO-optimised post that will (hopefully) show up in Google searches for more than a few days.
That being said, for the top travel bloggers, an investment of this type would possibly be worth it for a luxury property if the blogger is in the luxury travel niche. It could also be appropriate compensation for the blogger's time and expenses. The blogger would write a full blog post with beautiful, edited photos, promote across multiple social media platforms and their email list of engaged and interested potential customers. The blogger would probably spend hours equalling 3-4 full days work, and also need to be compensated for not only the costs of running a website, but photography equipment and software, and all other costs a self-employed person has! The property needs to ask for more information from the blogger to make the assessment though, and many places do ask for a lot more statistics rather than just followers.
I myself have absolutely no desire to do sponsored stays. I really would feel obliged to say only good things about the property. No matter how hard I would try to be impartial, everything would be seen in a good light because it's not being paid for. Also, the staff would know you were there to promote the property and the service received would likely be above and beyond the norm.
Anyway, just another point of view...