Awesome, congrats.
Just putting this out there: if you're generating that scale of value for agencies, you can often get them to agree to an arrangement which sounds like "$X per account you rep". Mental comparison for you: what's the largest agency you count as a client paying you? Would $250 times the number of accounts they rep be a substantially larger number than that? They probably make substantially more than that.
My brother works at a PPC agency. Typical client: a company you've never heard of in Chicago which does, without loss of generality, weatherproofing. They have a PPC budget of $IT_WOULD_BLOW_YOUR_MINDS_HN. Like many PPC companies, they charge (WLoG) 20% of spend every month. $250 doesn't make that account meaningfully lucrative and if you give them 1 extra conversion a month to brag about it's net profitable for the client.
I am aware of other marketing software companies which get into very cozy relationships with their favorite marketing agencies, to the tune of four to five figure checks monthly. That would, presumably, lift your average from $70 to an even happier number.
Bonus points: if you do it right, you can pitch this as a straight moneymaker to the agency, on some model like "You add a line-item to all your invoices of +$500 for $FOO_SOFT, so after we get our cut, that's $12,500 that your agency grosses which is totally free money to you."