I'd put it slightly differently.
Is the £26m/£30m Lamela a sufficient upgrade on the £1m Lennon, can we see the multiple times as good player we should have got for that.
I think you are being deliberately over simplistic in order to make a very bogus case.
You know it isn't that black and white. When we bought Bale for 10m (5+5) from Southampton would we have said that he was 10 times better than Lennon at 1m for the first 3 years of his time with us ?
The circumstances of transfers can vary massively and this dictates a price.
Was 26m a fair rate for Lamela, given al the circumstances, his age, his contract, his performances to date, his potential to improve and increase and reach current market values ?
I'd say it was on the expensive side for sure, but I can understand it in a maker place when Bale had just scored 6 goals more aged 24/25 and had been valued at 90m.
No one would argue that Lennon has been great value for his original 1m fee. But has he been value for his salary for 9 years ?
If Lamela does fulfil some of that potential and we make 20m form him, we can buy 20 Lennons. Part of our financial model is speculating on the transfer market. I have more problem with paying 6m + wages for a player who will not improve the first at all, has no potential to improve in ability or value and his skilset is replicated in the development group.