The answer in short is obviously yes.
250€ a month can be seen as price but only if you don't take the custom build into account. Also actually this should be limited to a certain amount of time / work.
And maybe you could think about a threshold model. But I don't know what you're actually wanting to achieve and this already off topic to me.
You have to see the 250€ as tax deductable because in the end as a company (and I am one) this is a reduction of profit. Hence it's the choice between paying you directly for something where I would have a direct benefit from or paying it to the state, which also holds benefits but ... anyhow.
So yes 250€ for pro support why not. I would even go further and limit this support because for 250€ a month you can barely eat and this model is not linear scalable :)