Hi

There is something you need to know

in their business strategy , they clearly dont want to target EU <-> EU market

so its normal if you see crazy prices for flying to HEL from another western european country but a regular price to LED despite the fact that both airports are really close (~200 miles helsinki to st petersburg)

For instance a random simulation , fly from GVA to HEL will cost 600 USD , but sames dates to LED will cost less than 200 usd

The only 3 places in northern europe which are not concerned by this ''rule'' are VNO , RIX and TLL (There is also MSQ but its another topic)

Also keep in mind that codeshares are generally more expensive with aeroflot , prices tend to be at least 25% higher in such cases

Last thing to mention is about algorithm , when they calculate prices, they decide how much to charge and it depends on many variables

But as most users are buying one way or return tickets so they wont make the extra effort to optimise their systems just for few complex requests . Therefore the system may show you a huge price or say it can't find what you want

In your case if you have an absolute need to pass by SVO , i would suggest you to use another airline , like air baltic , air france or klm and buy your GVA-XXX-SVO and HEL-XXX-GVA

Then between SVO and HEL use whatever you want , but it needs to be a separate ticket otherwise prices will go up

You will save money + time , and if you choose another skyteam airline you will earn miles and get segments