Amazon Product API: Offers from Amazon missing - amazon-product-api

Question

I am confused how the Amazon Product API works. For my example I used this ASIN (B00Y9S4V22) which is available in the german Amazon.
I requested the data from the API with the response Group "Large,OfferFull,Offers" and was confused because the only price it returns me is "1,80". On the Amazon Page itself it shows 2,37 (orderable with Prime).
As you can see in the response below it says that there are total 3 new (In the Summary in TotalNew) - which is correct. But in the Offer Listing I only have 1 of them - the cheapest. But my goal is to get the offer which is sold by Amazon it self / prime orderable / plus-product orderable. But these offers are missing completely.
When I open the "All Offers" link I get this result:
As you can see the amazon offer is listed there - but still missing in my response.
XML Response (I removed unnecessary properties)
<Items>
<Request>
<IsValid>True</IsValid>
<ItemLookupRequest>
<Condition>All</Condition>
<IdType>ASIN</IdType>
<ItemId>B00Y9S4V22</ItemId>
<ResponseGroup>Large</ResponseGroup>
<ResponseGroup>OfferFull</ResponseGroup>
<ResponseGroup>Offers</ResponseGroup>
<VariationPage>All</VariationPage>
</ItemLookupRequest>
</Request>
<Item>
<ASIN>B00Y9S4V22</ASIN>
<ParentASIN>B01HU1G8A2</ParentASIN>
<DetailPageURL>https://www.amazon.de/Westcott-00-Geodreieck-bruchsicher-transparent/dp/B00Y9S4V22?psc=1&SubscriptionId=AKIAJAD2WJOOQC6SJGWQ&tag=cheepah-21&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B00Y9S4V22</DetailPageURL>
<SalesRank>832</SalesRank>
<ItemAttributes>
<ListPrice>
<Amount>237</Amount>
<CurrencyCode>EUR</CurrencyCode>
<FormattedPrice>EUR 2,37</FormattedPrice>
</ListPrice>
</ItemAttributes>
<OfferSummary>
<LowestNewPrice>
<Amount>180</Amount>
<CurrencyCode>EUR</CurrencyCode>
<FormattedPrice>EUR 1,80</FormattedPrice>
</LowestNewPrice>
<TotalNew>3</TotalNew>
<TotalUsed>0</TotalUsed>
<TotalCollectible>0</TotalCollectible>
<TotalRefurbished>0</TotalRefurbished>
</OfferSummary>
<Offers>
<TotalOffers>1</TotalOffers>
<TotalOfferPages>1</TotalOfferPages>
<MoreOffersUrl>https://www.amazon.de/gp/offer-listing/B00Y9S4V22?SubscriptionId=AKIAJAD2WJOOQC6SJGWQ&tag=cheepah-21&linkCode=xm2&camp=2025&creative=12738&creativeASIN=B00Y9S4V22</MoreOffersUrl>
<Offer>
<Merchant>
<Name>mane Büroshop</Name>
</Merchant>
<OfferAttributes>
<Condition>New</Condition>
</OfferAttributes>
<OfferListing>
<OfferListingId>47YkU0Y7wnSskg8Uv7WqMgMXIxp3CsbATIFxuhiVJN3WRBaDRBRVgDtK4OIpe%2ByOIQQubWu4jlopsbF3uBH2AeWqyOFDpEGOLh7X%2BPjKwYsRTKgA7vy12yfzZyVVIY%2F10%2BrPSNeI24F8fo9qxj%2FLCgUdrVCFhI2a</OfferListingId>
<Price>
<Amount>180</Amount>
<CurrencyCode>EUR</CurrencyCode>
<FormattedPrice>EUR 1,80</FormattedPrice>
</Price>
<AmountSaved>
<Amount>57</Amount>
<CurrencyCode>EUR</CurrencyCode>
<FormattedPrice>EUR 0,57</FormattedPrice>
</AmountSaved>
<PercentageSaved>24</PercentageSaved>
<Availability>Versandfertig in 1 - 2 Werktagen</Availability>
<AvailabilityAttributes>
<AvailabilityType>now</AvailabilityType>
<MinimumHours>24</MinimumHours>
<MaximumHours>48</MaximumHours>
</AvailabilityAttributes>
<IsEligibleForSuperSaverShipping>0</IsEligibleForSuperSaverShipping>
<IsEligibleForPrime>0</IsEligibleForPrime>
</OfferListing>
</Offer>
</Offers>
</Item>
</Items>
And here is the Request:
<Arguments>
<Argument Name="AWSAccessKeyId" Value="---"></Argument>
<Argument Name="AssociateTag" Value="---"></Argument>
<Argument Name="Condition" Value="All"></Argument>
<Argument Name="IdType" Value="ASIN"></Argument>
<Argument Name="ItemId" Value="B00Y9S4V22"></Argument>
<Argument Name="Operation" Value="ItemLookup"></Argument>
<Argument Name="ResponseGroup" Value="Large,OfferFull,Offers"></Argument>
<Argument Name="Service" Value="AWSECommerceService"></Argument>
<Argument Name="Timestamp" Value="2018-10-30T22:14:08.000Z"></Argument>
</Arguments>
I know that there is a "ListPrice" but as far as I understand Amazon this is not always the price which is Amazon is selling it.

Answer 1

For anyone else who is looking for a solution:
You can also provide the argument "MerchantId" and set it to "Amazon". I am still confused why not all Offers are listed but when setting the argument "MerchantId" the response will provide the Amazon Offer (but no offer else)