Depending on specifications, 4070 will be acceptable to very good if TDP does not exceed ~300W. However, the deciding factor will be availability for street prices at or below reasonable MSRPs of the OEM models.

What prices are reasonable? (The best air cooling may add up to €100, the best water cooling €150, Noctua €200 but not €400.)

3070 had €500 MSRP and the speed of 2080TI at €1200 for good value on paper. Over earlier generations, prices increased above inflation countering this good value perception. 4070 with 320W and 3070 with 300W are in the same inefficiency tier; on the one hand that tier justifies the 3080 price level €700 while on the other hand that inefficiency counters it. TSMC wafers are somewhat more expensive but on average per card this increase is still peanuts and mostly pretence. The node shrink to 4nm should result in much faster speeds above a typical generational improvement but we also saw such for occasional earlier card generations. There is competition with AMD. 3000 street prices have been high but mostly due to mining and greed while many non-miners simply have not bought at those exaggerated prices. Nvidia etc. try to use them as pretence for raising 4000 prices but many endconsumers may continue not to buy. Nvidia has booked much TSMC wafer volume and must not waste it by setting greedy prices resulting in low demand.

In conclusion, there are reasons for lower, same or higher prices. Every price can be set but it will also determine demand. €400 and Nvidia cannot meet demand, €500 and many will be sold, €600 and demand will be good although less so while not everybody buys, €700 or above plus OEM model surcharges and many will pass again on the next generation. Hence I think €550 - 600 is reasonable for maximal profit during a two years term provided always as good an availability as for every ordinary electronic product. If, however, MSRP will be a lie again, without miners, Nvidia will get a shitstorm unheard of and may lose its brand reputation.